A controlled trial of a killed Haemophilus influenzae vaccine for prevention of acute exacerbations of chronic bronchitis M. K. Tandon Thoracic Physician, Thoracic Division, Repatriation Gtneral Hospital, Pri th, WA
V. Gebski Director of Statistics Department, Statistical Laboratory, Macqudrie University, NSW
Abstract: Sixty-four patients with chronic bronchitis with a history of recurrent respiratory tract infections were admitted to a double-blind randomised controlled study in which the efficacy of an oral vaccine containing killed Haemophilus influenzae in preventing acute exacerbations of chronic bronchitis was compared with placebo. Patients given vaccine developed fewer acute infective episodes. Although the numbers of patients who required antibiotic therapy in the two groups were not significantly different, the number of antibiotic prescriptions given to the vaccinated group of patients was significantly less than that required by the control group. A reduction in colonisation with HaemophiZus infzuenzae occurred in the active group, which was maximal 14 weeks after the onset of the study. (Aust NZ J Med 1991; 21: 427-432.) Key words: Haemophilus influenme, chronic bronchitis, oral vaccine, controlled trial.
INTRODUCTION Acute infective exacerbations of chronic bronchitis play an important role in the morbidity and mortality of patients with chronic bronchitis. These infective episodes are commonly bacterial infections, often due to nontypable Haemophilus influenzae. Less commonly other pathogens such as Streptococcus pneum ~ n i a eand , ~ Branhamella catarrhali~~ contribute to the pathogenesis of acute bronchitis. Antibiotic therapy, while important in the management of these infective episodes,' may determine nosocomial and appearance of antibiotic resistant b a ~ t e r i a In . ~ view of this, immunisation against H. influenzae of patients with chronic bronchitis who are susceptible to recurrent acute infective episodes would be a logical approach to their management. A study of oral immunisation with killed H. influenzae reported protection against recurrent acute infective episodes in patients with chronic obstructive airways disease"C0AD). This randomised double-blind controlled study was
designed to find out whether oral immunisation of patients, with documented chronic bronchitis and recurrent respiratory tract infections, using a killed H . infhenzae vaccine compared with placebo, would reduce the frequency of infective episodes of bronchitis, reduce the need for antibiotics and decrease the carriage rate of the putative pathogen.
MATERIALS AND METHODS Patient Population Seventy-seven patients with chronic bronchitis, who had been documented to be susceptible to recurrent respiratory tract infections, were recruited from the Chest Clinic, Repatriation General Hospital, Hollywood, Western Australia. Consent in writing from all patients was obtained on a form approved by the Ethics Committee of the hospital. Ten patients were withdrawn from the study because of failure to attend the clinic for regular follow-up. Seven of these were in the placebo group and three were given active treatment.
Keprint requesrs to: Dr M. K. Tandon, Repatriation General Hospital, Monash Avenue, Hollywood WA 6009, Australia. A CONTROLI.ED T R I A L OF H. INF1,UENZAE VACCINE
Aust NZ J Med 1991; 21
427
TABLE 1 Demographic Data
No of patients completing Male female Age (yrs) mean range Smoking now previous never FEVl mean range
vc
mean range
Active
Placebo
31 22 9
33 30 3
73 1 48-93
71 1 60-88
4 21 6
9 24 0
0 96 047-313
0 89 027218
182 0 86-3 70
2 00 1 29-3 67
Three patients given vaccine died during the study period. Details of the sixty-four patients who completed the study are summarised in Table 1. One of the six patients who had never smoked had bronchiectasis and five others had chronic bronchial asthma and were susceptible to recurrent respiratory tract infections.
term antibiotics were excluded. At the time of entry, physical examination and a comprehensive questionnaire (ATS-DLD78) were completed. Lung function was assessed by spirometry and sputum samples were collected for microbiological examination. Subsequent assessments by the investigator were at 42,84 and 168 days when sputum samples were collected and a followup respiratory questionnaire was completed. For every acute lower respiratory tract infection, an ‘infection questionnaire’ was completed with the assistance of the patient’s primary care physician and, whenever possible, sputum was collected for microbiological examination before treatment with antibiotics was started. Acute infective episodes were defined as increase in volume and purulence of sputum, usually associated with increase in breathlessness andor fever requiring treatment with antibiotics. The diagnosis of infective episodes as defined above was made by the patient’s primary care physician. Some of the reported infections were not treated with antibiotics as their severity was mild and self limiting. T h e trial protocol consisted of administration of three courses of the active or placebo tablets at 0, 28 and 56 days. Each course consisted of two tablets taken one hour before breakfast each day for three consecutive days. All of the patients had access to the investigator throughout the study and thus full documentation of all infective episodes was maintained. Any patient who did not attend the clinic for regular follow-up or give adequate history of infective episodes was withdrawn from the study. For purposes of analysis, the incidence of infections, number of antibiotic courses and microbiology results were grouped into two three-month periods to determine any effect of time on differences induced by the active agent when compared with placebo. Recurrent infections were defined as infections if recurring within two weeks of a previous infection.
Trial Design A prospective double-blind, placebo controlled trial was conducted during the winter months of 1988. The patients were randomly allocated to receive either active enteric coated tablets containing 10” killed H . influenzae (BroncostatTM(formerly Rhone-Poulenc Rorer), Auspharm International Limited, Australia) or matched placebo tablets with lactose substituted for the bacteria. The bacilli in the active tablet were formalin-killed non-serotypable biotype-1 H. influenzae. The randomisation chart for the study was prepared by the hospital pharmacist who kept the trial code. Microbiological Methods At the start of the study each patient was assessed Sputa were liquefied in an equal volume of buffered by the investigator for suitability for entry into the N-acetyl L-cysteine and agitated for 15 minutes. 10 pL study. The criteria for inclusion into the study were of liquefied sputum was then diluted in 2 0 m L of any one or more of the following: distilled water. This 1:2000dilution was used to inocuHistory of chronic bronchitis (Medical Research late one plate each of MacConkey agar, blood agar, Council [MRC] criteria’) and at least two acute infecand chocolate blood agar with 14.3% (wlv) Bacitracin tive episodes per year for more than three years. (Sigma, USA). All plates were then incubated in 5-1070 Evidence of severe chronic obstructive airways COz at 37°C for 18-48 hours. Colonies morphologidisease (COAD) on the basis of one second forced cally resembling H. influenzae on blood or chocolate expiratory volume (FEV,) being less than 1 litre blood agar were identified by X and V requirements together with at least two acute infective episodes per on Columbia agar base medium. Base media was year. obtained from Oxoid, United Kingdom. All sputa were More than three isolations of H. influenzae on examined for leucocytes and bacteria using Gram microbiological examination of sputum in the past two stained smears. years together with history of recurrent respiratory tract infections. Symptom Scores Patients with COAD who did not have a history of The patient’s assessment of the eficacy of treatment was recorded using a visual analogue scale (VAS) only recurrent respiratory tract infections and those on long428 Aust NZ J Med 1991; 21 TANDON AND GEBSKI
at 24 weeks. T h e VAS rating was made by asking the patients to give a score on a - 10 to 10 scale of their overall clinical condition at 24 weeks, compared to
+
their condition prior to the start of the study, which was rated as zero. If they felt better, a plus score was noted, zero if unchanged and a minus score if they felt worse.
Statistical Methods The number of reported infections, the number of patients developing infections and the number of courses of antibiotics in the two treatment groups were tested for any significant difference. T h e number of reported infections and the number of courses of antibiotics in the two groups were analysed using multiple Poisson regression," allowing for the effect of confounding factors such as age, smoking and sex to be adjusted in the treatment comparisons. The choice of Poisson and logistic regression was guided by the nature of the problem at hand - viz, comparison of rates of infection and occurrences. For data of this type, the use of the more conventional methods such as chi-squared etc, are not as powerful as those used. Unadjusted 2x2 contingency table comparisons for the proportion of patients developing infections and the proportion requiring antibiotics in periods one and two were analysed using the conditional binomial exact test." Differences in the sputum carriage rates of H. influenzae were tested by transforming the data to normality using logits [ I n (p/l-p)]. Thereafter an analysis of covariance, using multiple regression, was performed to test for parallelism and colinearity of treatment effects. Patients' symptom scores were tested using the Wilcoxon rank sum test.
RESULTS The number of reported infections (incidence) and the number of patients developing infections (occurrence) in the two treatment groups during the two periods are shown in Table 2. The difference in the incidence of infection in the two treatment groups failed to reach a level of significance on a two tailed test (p = 0.077). T h e age of patients in the two groups played a significant role in influencing the number of reported infections (p = 0.032). T h e analysis showed that the younger the person, the lower the number of infections present. When the incidence rate was corrected for age, it remained non-significant (p = 0.116). The occurrence of infections in the treated group of patients was significantly less than that in the placebo group (p = 0.024), with a relative risk of2.27 and 95% confidence interval for the relative risk being 1.114-4.625. Other potential confounding factors consisting of age, sex, and smoking history showed no significant difference in the two groups of patients. The reduced A CON'1ROLI.ED TRIAL OF H I~VFLCEN%AEVACCINE
TABLE 2 Incidence and Occurrence of Infections Vaccine
Placebo
Number of patients
31 33 period 1 * period 2l period 1 * period 2 t 26 18 Number of infections 36 30 (incidence) 17 11 22 21 Number of patients with infection (occurrence) ' 0 3 months of study '3 6 months of studv
occurrence of infections was observed mainly in period I1 (p = 0.026). Table 2 describes the breakdown of these parameters by treatment group. The number of courses of antibiotics given to patients receiving the active agent was significantly less than those given to patients receiving placebo (p = 0.007) (Table 3). Differences in the ages of patients in two groups again played a significant role in the differences observed (p = 0.049). When the analysis of differences in courses of antibiotics was corrected for age, the conclusion remained unchanged (p = 0.042). Although the number of patients who received antibiotics in the active group was less than in the placebo, the differences were not significant (p = 0.242). Analysis of numbers of reported infections in the two groups with respect to bacterial isolates showed that in the active group, numbers of infections in those patients from whose sputum H. influenzue were isolated before or during an acute infective episode were significantly higher than those from whose sputum H. influenzae were not isolated @=0.011) (Table 4). These differences were not seen in the placebo group. There was no period effect (p = 0.256). Similarly, analysis of antibiotic prescriptions in the two study groups showed that the patients who were carriers of H. influenzae in the active group required a significantly higher number of courses of antibiotics than those from whose sputum H. influenzae were not isolated @=0.022) (Table 4). On the other hand, patients in the placebo group did not show these differences in antibiotic prescriptions. TABLE 3 Antibiotic Therapy
Active
Placebo
31 33 period 1 * period 2 1 period 1 * period 2' 26 19 36 43 Number of courses antibiotics 14 11 22 18 Number of patients receiving antibiotics Number of patients
'0 3 months of study
' 3 6 months of study
Aust NZ J Med 1991; 21
429
period symptom scores for individual parameters, ie breathlessness, cough and sputum, though higher in the active group, were not statistically significant. The ten patients (three on active and seven on placebo) who did not complete the study were compared for their various characteristics by intention to treat and no significant differences emerged. If we assume that the number of infections did not change over the follow-up period, then there is little change in the result if an analysis by intention to treat is performed.
I ACTIVE 40
10:
PRE
=
I
4
'
1
8
.
I
12
.
I
16
-
I
20
*
Side Effects In the active group, three complained of transient deterioration of respiratory symptoms, such as increased dyspnoea and/or cough for up to three days; one had diarrhoea, and four felt generally unwell. In the placebo group, six complained of abdominal pain and diarrhoea, three felt unwell and one noticed some increase in cough. These side effects were reported on the 2nd or 3rd day after lst, 2nd or 3rd treatment. Three patients given vaccine died during the trial period. Two had terminal respiratory infection on clinical grounds and no autopsy was performed. These terminal events occurred five and 18 weeks from entry into the study. The third patient died suddenly from ruptured aneurysm; autopsy was carried out and there was no evidence of active infection in the respiratory tract. This patient was a chronic carrier of H. influenzue. A statistical test for difference in morbidity rates between the two groups is non-significant @ = 0.081 from the conditional binomial exact test).
1
:
(Weeks)
STUDY PERIOD
Figure f: Haemophiliis influenzae rates during the four study periods in patients given active agent and placebo.
Following treatment in the active group there was a reduction in the percentage carriage for H. influenme at six, 14 and 24 weeks. Although this trend is not statistically significantly different @ = 0.418), it is of clinical relevance (Figure 1). In terms of global assessment for general well-being, the patients receiving the active agent overall had higher median scores for VAS than those reported by placebo group (p = 0.09) (Table 5). For the entire study
DISCUSSION This prospective randomised double-blind placebo controlled trial of a killed H. influenzae oral vaccine in a group of elderly subjects with chronic bronchitis and COAD demonstrated protection against the occurrence of acute infections, a reduction in the number
TABLE 4 Number of Infections and Antibiotics in Relation to Microbiology Active N
No of infections in the group with H mfluenzae isolated from sputum No ot infections in patients without H mfluenzae in sputum No of antibiotic courses in the group with H mfluenzae in sputum No of antibiot c courses in patients without H infiuenzae in sputum
430
~
~
~ Period t 1 ~
f Period 2
9
13
a
22
13
10
9
15
8
22
11
11
Aust NZ J Med 1991; 2 1
Number of patients
1:;
14
Placebo Period 1
Period 2
20
17
;: : 17
22 TANDON AND GEBSKI
TABLE 5
Changes in Symptom Scores at 24 Weeks from Basal Zero Value Symptoms
Global Breathlessness Cough Sputum
Vaccine Median score
Placebo Median score
5.0 0 40 40
25 0 25 25
'p
0 09 0.43
0.42 0.52
of courses of antibiotic therapy prescribed and a transient reduction in the level of colonisation by H. influenzae. Maximum protection occurred in the second threemonth period of the study because the reductions in the number of reported infections and the number of patients reporting infections were predominantly seen during this second period. Improvement in these parameters was more impressively reflected in the reduction of antibiotic prescriptions required by the immunised group of patients. There was 28% less chance of getting a prescription for any particular infection episode for those taking the active vaccine. One explanation for the disproportionate reduction in prescription rate is that individual episodes of acute bronchitis were less severe in those taking active vaccine and thus were less likely to be prescribed antibiotics. Transient reduction in colonisation rate of the sputum with H. influenzue was only seen in the active group and this correlated with protection against acute episodes of bronchitis. A similar trend has been reported previously.' Recent studies in Australian subjects with chronic bronchitis have shown that H. influenzae is commonly found within the bronchi and that when present it constitutes greater than 90% of the total aerobic bacterial population.'2 Thus, while acute bronchitis represents a mucosal inflammatory response to a polymicrobial colonisation of the bronchus, reduction in the H. influenzae load may be expected to give a significant benefit with respect to preventing acute bronchitis. Of interest was the observation in this study that suggested a non-specific effect of the vaccine in providing protection in subjects not colonised with H. influenzue. This observation has been noted in another trial of this oral vaccine (Lehman, personal communication). This appears to contrast with data obtained in an animal mode1I3 which demonstrated wide cross protection amongst different H. influenzae isolates, but little cross reactivity between different bacterial species. This animal model however, demonstrated that the effector mechanism for bacterial clearance was an enhanced recruitment of neutrophils, which phagocytose bacteria within the bronchus lumen in an indiscriminate fashion. Antigen is required within the A CONTROILED TRIAL OF 1I INFI.UfiNL4E VACCINE
bronchus to recruit immune clearance initiated through the gut associated lymphoid system. Colonisation of the bronchus with H. influenzae is a variable phenomenon, and it may be that patients without H. infhenzae when treated had intermittent exposure to H. znfhenzue. Further, it should be noted that the nonvaccinated patients, irrespective of bacterial isolation characteristics, had a greater number of infections and required more frequent antibiotic prescriptions. It is important to note that by the 24th week, H. injlucnzue had begun to recolonise patients who had previously shown a reduction in colonisation, maximal at 14 weeks. This observation is in keeping with the ' ~ mucosal immuearlier finding of Mestecky et ~ 1 . that nity is of short duration. This has important clinical implications because if the vaccine is to be used for prevention of acute infections in patients with chronic bronchitis then it would have to be given at six to eight monthly intervals. Unlike the trial of Broncostat,' this trial began in the middle of winter and yet vaccination was effective. Hence, it suggests that the vaccine rn can be given at any time of the year. Acknowledgements We wish to thank staff of the Microbiology Department, Repatriation General Hospital, Hollywood, Western Australia for sputum microbiological examinations. We are grateful to Auspharm International Ltd for providing the BroncostatTM and placebo tablets for this study. Date of submission: 12 February 1990
References I . 'l'ager I, Speizer FE. Role of infection in chronic bronchitis. N Engl J Med 1975; 292: 563-71. 2. Burns MW, May JR. Haetnophilus influenzae precipitins in the serum of patients with chronic bronchial disorders. Lancet 1967; i: 354-8. 3. Miller DP, Jones R. T h e bacterial flora of the upper respiratory tract and sputum of working men. J Path Bact 1964; 87: 182-6. 4. Waters AJ, Steinfort CL, Andrew JH. Brunhatnellu curarrhalis, a respiratory tract pathogen. Aust NZ J Med 1985; 15: 579-84. 5. May JR. Antibiotics in chronic bronchitis. Lancet 1953; ii: 899-902. 6. Graybill JR, Marshall I.W, Charache, ' l Wallace CK, iMelvin VB. Nosocomial pneumonia. A continuing major problem. Am Rev Respir Dis 1973; 108: 1130-40. 7. Gopalakrishna KV, Lerner PI. Tetracyclirie-resistant pneumococci: increasing incidence and cross resistance to newer tetracyclines. Am Rev Respir Dis 1973; 108: 1007-10. 8. Clancy R, Cripps A, Murree-Allen K, Yeung S, Engel M. Oral immunization with killed Haemophilus ztijluenzue for protection against acute bronchitis in chronic obstructive lung discase. Lancet 1985; ii: 1395-7. 9. Medical Research Council. Definition and classification of chronic hronchitis for clinical and epidemiological purposes. Lancet 1965; i: 775-9. 10. Adena MA, Wilson SR. Generalized linear models in epidemiological research case-control studies. INSTAT Foundation, Sydney, 1982. Aust N Z J Med 1991; 21
431
11. Rice WR. A new probability model for determining exact pvalues for 2 x 2 contingency tables when comparing binomial proportions. Biometrics 1988; 44: 1-14. 12. Butt HL, Clancy RL, Cripps AW, Murree-Allen K, Saunders NA, Sutherland DC, Hensley MJ. Bacterial colonisation of the respiratory tract in chronic bronchitis. Aust NZ J Med (1990; 20: 35-8. 13. Wallace FJ, Clancy RL, Cripps AW. An animal model demon-
432
Aust NZ J Med 1991; 2 1
stration of enhanced clearance of nontypable Haemophilus injhenzae from the respiratory tract after antigen stimulation of gut-associated lymphoid tissue. Am Rev Resp Dis 1989; 140: 311-6. 14. Mestecky J, McGhee JR, Arnold RR, Michaelek SM, Prince SJ, Babb JL. Selective induction of an immune response in human external secretions by ingestion of bacterial antigen. J Clin Invest 1978; 61: 731-7.
TANDON AND GEBSKI
V. Gebski Director of Statistics Department, Statistical Laboratory, Macqudrie University, NSW
Abstract: Sixty-four patients with chronic bronchitis with a history of recurrent respiratory tract infections were admitted to a double-blind randomised controlled study in which the efficacy of an oral vaccine containing killed Haemophilus influenzae in preventing acute exacerbations of chronic bronchitis was compared with placebo. Patients given vaccine developed fewer acute infective episodes. Although the numbers of patients who required antibiotic therapy in the two groups were not significantly different, the number of antibiotic prescriptions given to the vaccinated group of patients was significantly less than that required by the control group. A reduction in colonisation with HaemophiZus infzuenzae occurred in the active group, which was maximal 14 weeks after the onset of the study. (Aust NZ J Med 1991; 21: 427-432.) Key words: Haemophilus influenme, chronic bronchitis, oral vaccine, controlled trial.
INTRODUCTION Acute infective exacerbations of chronic bronchitis play an important role in the morbidity and mortality of patients with chronic bronchitis. These infective episodes are commonly bacterial infections, often due to nontypable Haemophilus influenzae. Less commonly other pathogens such as Streptococcus pneum ~ n i a eand , ~ Branhamella catarrhali~~ contribute to the pathogenesis of acute bronchitis. Antibiotic therapy, while important in the management of these infective episodes,' may determine nosocomial and appearance of antibiotic resistant b a ~ t e r i a In . ~ view of this, immunisation against H. influenzae of patients with chronic bronchitis who are susceptible to recurrent acute infective episodes would be a logical approach to their management. A study of oral immunisation with killed H. influenzae reported protection against recurrent acute infective episodes in patients with chronic obstructive airways disease"C0AD). This randomised double-blind controlled study was
designed to find out whether oral immunisation of patients, with documented chronic bronchitis and recurrent respiratory tract infections, using a killed H . infhenzae vaccine compared with placebo, would reduce the frequency of infective episodes of bronchitis, reduce the need for antibiotics and decrease the carriage rate of the putative pathogen.
MATERIALS AND METHODS Patient Population Seventy-seven patients with chronic bronchitis, who had been documented to be susceptible to recurrent respiratory tract infections, were recruited from the Chest Clinic, Repatriation General Hospital, Hollywood, Western Australia. Consent in writing from all patients was obtained on a form approved by the Ethics Committee of the hospital. Ten patients were withdrawn from the study because of failure to attend the clinic for regular follow-up. Seven of these were in the placebo group and three were given active treatment.
Keprint requesrs to: Dr M. K. Tandon, Repatriation General Hospital, Monash Avenue, Hollywood WA 6009, Australia. A CONTROLI.ED T R I A L OF H. INF1,UENZAE VACCINE
Aust NZ J Med 1991; 21
427
TABLE 1 Demographic Data
No of patients completing Male female Age (yrs) mean range Smoking now previous never FEVl mean range
vc
mean range
Active
Placebo
31 22 9
33 30 3
73 1 48-93
71 1 60-88
4 21 6
9 24 0
0 96 047-313
0 89 027218
182 0 86-3 70
2 00 1 29-3 67
Three patients given vaccine died during the study period. Details of the sixty-four patients who completed the study are summarised in Table 1. One of the six patients who had never smoked had bronchiectasis and five others had chronic bronchial asthma and were susceptible to recurrent respiratory tract infections.
term antibiotics were excluded. At the time of entry, physical examination and a comprehensive questionnaire (ATS-DLD78) were completed. Lung function was assessed by spirometry and sputum samples were collected for microbiological examination. Subsequent assessments by the investigator were at 42,84 and 168 days when sputum samples were collected and a followup respiratory questionnaire was completed. For every acute lower respiratory tract infection, an ‘infection questionnaire’ was completed with the assistance of the patient’s primary care physician and, whenever possible, sputum was collected for microbiological examination before treatment with antibiotics was started. Acute infective episodes were defined as increase in volume and purulence of sputum, usually associated with increase in breathlessness andor fever requiring treatment with antibiotics. The diagnosis of infective episodes as defined above was made by the patient’s primary care physician. Some of the reported infections were not treated with antibiotics as their severity was mild and self limiting. T h e trial protocol consisted of administration of three courses of the active or placebo tablets at 0, 28 and 56 days. Each course consisted of two tablets taken one hour before breakfast each day for three consecutive days. All of the patients had access to the investigator throughout the study and thus full documentation of all infective episodes was maintained. Any patient who did not attend the clinic for regular follow-up or give adequate history of infective episodes was withdrawn from the study. For purposes of analysis, the incidence of infections, number of antibiotic courses and microbiology results were grouped into two three-month periods to determine any effect of time on differences induced by the active agent when compared with placebo. Recurrent infections were defined as infections if recurring within two weeks of a previous infection.
Trial Design A prospective double-blind, placebo controlled trial was conducted during the winter months of 1988. The patients were randomly allocated to receive either active enteric coated tablets containing 10” killed H . influenzae (BroncostatTM(formerly Rhone-Poulenc Rorer), Auspharm International Limited, Australia) or matched placebo tablets with lactose substituted for the bacteria. The bacilli in the active tablet were formalin-killed non-serotypable biotype-1 H. influenzae. The randomisation chart for the study was prepared by the hospital pharmacist who kept the trial code. Microbiological Methods At the start of the study each patient was assessed Sputa were liquefied in an equal volume of buffered by the investigator for suitability for entry into the N-acetyl L-cysteine and agitated for 15 minutes. 10 pL study. The criteria for inclusion into the study were of liquefied sputum was then diluted in 2 0 m L of any one or more of the following: distilled water. This 1:2000dilution was used to inocuHistory of chronic bronchitis (Medical Research late one plate each of MacConkey agar, blood agar, Council [MRC] criteria’) and at least two acute infecand chocolate blood agar with 14.3% (wlv) Bacitracin tive episodes per year for more than three years. (Sigma, USA). All plates were then incubated in 5-1070 Evidence of severe chronic obstructive airways COz at 37°C for 18-48 hours. Colonies morphologidisease (COAD) on the basis of one second forced cally resembling H. influenzae on blood or chocolate expiratory volume (FEV,) being less than 1 litre blood agar were identified by X and V requirements together with at least two acute infective episodes per on Columbia agar base medium. Base media was year. obtained from Oxoid, United Kingdom. All sputa were More than three isolations of H. influenzae on examined for leucocytes and bacteria using Gram microbiological examination of sputum in the past two stained smears. years together with history of recurrent respiratory tract infections. Symptom Scores Patients with COAD who did not have a history of The patient’s assessment of the eficacy of treatment was recorded using a visual analogue scale (VAS) only recurrent respiratory tract infections and those on long428 Aust NZ J Med 1991; 21 TANDON AND GEBSKI
at 24 weeks. T h e VAS rating was made by asking the patients to give a score on a - 10 to 10 scale of their overall clinical condition at 24 weeks, compared to
+
their condition prior to the start of the study, which was rated as zero. If they felt better, a plus score was noted, zero if unchanged and a minus score if they felt worse.
Statistical Methods The number of reported infections, the number of patients developing infections and the number of courses of antibiotics in the two treatment groups were tested for any significant difference. T h e number of reported infections and the number of courses of antibiotics in the two groups were analysed using multiple Poisson regression," allowing for the effect of confounding factors such as age, smoking and sex to be adjusted in the treatment comparisons. The choice of Poisson and logistic regression was guided by the nature of the problem at hand - viz, comparison of rates of infection and occurrences. For data of this type, the use of the more conventional methods such as chi-squared etc, are not as powerful as those used. Unadjusted 2x2 contingency table comparisons for the proportion of patients developing infections and the proportion requiring antibiotics in periods one and two were analysed using the conditional binomial exact test." Differences in the sputum carriage rates of H. influenzae were tested by transforming the data to normality using logits [ I n (p/l-p)]. Thereafter an analysis of covariance, using multiple regression, was performed to test for parallelism and colinearity of treatment effects. Patients' symptom scores were tested using the Wilcoxon rank sum test.
RESULTS The number of reported infections (incidence) and the number of patients developing infections (occurrence) in the two treatment groups during the two periods are shown in Table 2. The difference in the incidence of infection in the two treatment groups failed to reach a level of significance on a two tailed test (p = 0.077). T h e age of patients in the two groups played a significant role in influencing the number of reported infections (p = 0.032). T h e analysis showed that the younger the person, the lower the number of infections present. When the incidence rate was corrected for age, it remained non-significant (p = 0.116). The occurrence of infections in the treated group of patients was significantly less than that in the placebo group (p = 0.024), with a relative risk of2.27 and 95% confidence interval for the relative risk being 1.114-4.625. Other potential confounding factors consisting of age, sex, and smoking history showed no significant difference in the two groups of patients. The reduced A CON'1ROLI.ED TRIAL OF H I~VFLCEN%AEVACCINE
TABLE 2 Incidence and Occurrence of Infections Vaccine
Placebo
Number of patients
31 33 period 1 * period 2l period 1 * period 2 t 26 18 Number of infections 36 30 (incidence) 17 11 22 21 Number of patients with infection (occurrence) ' 0 3 months of study '3 6 months of studv
occurrence of infections was observed mainly in period I1 (p = 0.026). Table 2 describes the breakdown of these parameters by treatment group. The number of courses of antibiotics given to patients receiving the active agent was significantly less than those given to patients receiving placebo (p = 0.007) (Table 3). Differences in the ages of patients in two groups again played a significant role in the differences observed (p = 0.049). When the analysis of differences in courses of antibiotics was corrected for age, the conclusion remained unchanged (p = 0.042). Although the number of patients who received antibiotics in the active group was less than in the placebo, the differences were not significant (p = 0.242). Analysis of numbers of reported infections in the two groups with respect to bacterial isolates showed that in the active group, numbers of infections in those patients from whose sputum H. influenzue were isolated before or during an acute infective episode were significantly higher than those from whose sputum H. influenzae were not isolated @=0.011) (Table 4). These differences were not seen in the placebo group. There was no period effect (p = 0.256). Similarly, analysis of antibiotic prescriptions in the two study groups showed that the patients who were carriers of H. influenzae in the active group required a significantly higher number of courses of antibiotics than those from whose sputum H. influenzae were not isolated @=0.022) (Table 4). On the other hand, patients in the placebo group did not show these differences in antibiotic prescriptions. TABLE 3 Antibiotic Therapy
Active
Placebo
31 33 period 1 * period 2 1 period 1 * period 2' 26 19 36 43 Number of courses antibiotics 14 11 22 18 Number of patients receiving antibiotics Number of patients
'0 3 months of study
' 3 6 months of study
Aust NZ J Med 1991; 21
429
period symptom scores for individual parameters, ie breathlessness, cough and sputum, though higher in the active group, were not statistically significant. The ten patients (three on active and seven on placebo) who did not complete the study were compared for their various characteristics by intention to treat and no significant differences emerged. If we assume that the number of infections did not change over the follow-up period, then there is little change in the result if an analysis by intention to treat is performed.
I ACTIVE 40
10:
PRE
=
I
4
'
1
8
.
I
12
.
I
16
-
I
20
*
Side Effects In the active group, three complained of transient deterioration of respiratory symptoms, such as increased dyspnoea and/or cough for up to three days; one had diarrhoea, and four felt generally unwell. In the placebo group, six complained of abdominal pain and diarrhoea, three felt unwell and one noticed some increase in cough. These side effects were reported on the 2nd or 3rd day after lst, 2nd or 3rd treatment. Three patients given vaccine died during the trial period. Two had terminal respiratory infection on clinical grounds and no autopsy was performed. These terminal events occurred five and 18 weeks from entry into the study. The third patient died suddenly from ruptured aneurysm; autopsy was carried out and there was no evidence of active infection in the respiratory tract. This patient was a chronic carrier of H. influenzue. A statistical test for difference in morbidity rates between the two groups is non-significant @ = 0.081 from the conditional binomial exact test).
1
:
(Weeks)
STUDY PERIOD
Figure f: Haemophiliis influenzae rates during the four study periods in patients given active agent and placebo.
Following treatment in the active group there was a reduction in the percentage carriage for H. influenme at six, 14 and 24 weeks. Although this trend is not statistically significantly different @ = 0.418), it is of clinical relevance (Figure 1). In terms of global assessment for general well-being, the patients receiving the active agent overall had higher median scores for VAS than those reported by placebo group (p = 0.09) (Table 5). For the entire study
DISCUSSION This prospective randomised double-blind placebo controlled trial of a killed H. influenzae oral vaccine in a group of elderly subjects with chronic bronchitis and COAD demonstrated protection against the occurrence of acute infections, a reduction in the number
TABLE 4 Number of Infections and Antibiotics in Relation to Microbiology Active N
No of infections in the group with H mfluenzae isolated from sputum No ot infections in patients without H mfluenzae in sputum No of antibiotic courses in the group with H mfluenzae in sputum No of antibiot c courses in patients without H infiuenzae in sputum
430
~
~
~ Period t 1 ~
f Period 2
9
13
a
22
13
10
9
15
8
22
11
11
Aust NZ J Med 1991; 2 1
Number of patients
1:;
14
Placebo Period 1
Period 2
20
17
;: : 17
22 TANDON AND GEBSKI
TABLE 5
Changes in Symptom Scores at 24 Weeks from Basal Zero Value Symptoms
Global Breathlessness Cough Sputum
Vaccine Median score
Placebo Median score
5.0 0 40 40
25 0 25 25
'p
0 09 0.43
0.42 0.52
of courses of antibiotic therapy prescribed and a transient reduction in the level of colonisation by H. influenzae. Maximum protection occurred in the second threemonth period of the study because the reductions in the number of reported infections and the number of patients reporting infections were predominantly seen during this second period. Improvement in these parameters was more impressively reflected in the reduction of antibiotic prescriptions required by the immunised group of patients. There was 28% less chance of getting a prescription for any particular infection episode for those taking the active vaccine. One explanation for the disproportionate reduction in prescription rate is that individual episodes of acute bronchitis were less severe in those taking active vaccine and thus were less likely to be prescribed antibiotics. Transient reduction in colonisation rate of the sputum with H. influenzue was only seen in the active group and this correlated with protection against acute episodes of bronchitis. A similar trend has been reported previously.' Recent studies in Australian subjects with chronic bronchitis have shown that H. influenzae is commonly found within the bronchi and that when present it constitutes greater than 90% of the total aerobic bacterial population.'2 Thus, while acute bronchitis represents a mucosal inflammatory response to a polymicrobial colonisation of the bronchus, reduction in the H. influenzae load may be expected to give a significant benefit with respect to preventing acute bronchitis. Of interest was the observation in this study that suggested a non-specific effect of the vaccine in providing protection in subjects not colonised with H. influenzue. This observation has been noted in another trial of this oral vaccine (Lehman, personal communication). This appears to contrast with data obtained in an animal mode1I3 which demonstrated wide cross protection amongst different H. influenzae isolates, but little cross reactivity between different bacterial species. This animal model however, demonstrated that the effector mechanism for bacterial clearance was an enhanced recruitment of neutrophils, which phagocytose bacteria within the bronchus lumen in an indiscriminate fashion. Antigen is required within the A CONTROILED TRIAL OF 1I INFI.UfiNL4E VACCINE
bronchus to recruit immune clearance initiated through the gut associated lymphoid system. Colonisation of the bronchus with H. influenzae is a variable phenomenon, and it may be that patients without H. infhenzae when treated had intermittent exposure to H. znfhenzue. Further, it should be noted that the nonvaccinated patients, irrespective of bacterial isolation characteristics, had a greater number of infections and required more frequent antibiotic prescriptions. It is important to note that by the 24th week, H. injlucnzue had begun to recolonise patients who had previously shown a reduction in colonisation, maximal at 14 weeks. This observation is in keeping with the ' ~ mucosal immuearlier finding of Mestecky et ~ 1 . that nity is of short duration. This has important clinical implications because if the vaccine is to be used for prevention of acute infections in patients with chronic bronchitis then it would have to be given at six to eight monthly intervals. Unlike the trial of Broncostat,' this trial began in the middle of winter and yet vaccination was effective. Hence, it suggests that the vaccine rn can be given at any time of the year. Acknowledgements We wish to thank staff of the Microbiology Department, Repatriation General Hospital, Hollywood, Western Australia for sputum microbiological examinations. We are grateful to Auspharm International Ltd for providing the BroncostatTM and placebo tablets for this study. Date of submission: 12 February 1990
References I . 'l'ager I, Speizer FE. Role of infection in chronic bronchitis. N Engl J Med 1975; 292: 563-71. 2. Burns MW, May JR. Haetnophilus influenzae precipitins in the serum of patients with chronic bronchial disorders. Lancet 1967; i: 354-8. 3. Miller DP, Jones R. T h e bacterial flora of the upper respiratory tract and sputum of working men. J Path Bact 1964; 87: 182-6. 4. Waters AJ, Steinfort CL, Andrew JH. Brunhatnellu curarrhalis, a respiratory tract pathogen. Aust NZ J Med 1985; 15: 579-84. 5. May JR. Antibiotics in chronic bronchitis. Lancet 1953; ii: 899-902. 6. Graybill JR, Marshall I.W, Charache, ' l Wallace CK, iMelvin VB. Nosocomial pneumonia. A continuing major problem. Am Rev Respir Dis 1973; 108: 1130-40. 7. Gopalakrishna KV, Lerner PI. Tetracyclirie-resistant pneumococci: increasing incidence and cross resistance to newer tetracyclines. Am Rev Respir Dis 1973; 108: 1007-10. 8. Clancy R, Cripps A, Murree-Allen K, Yeung S, Engel M. Oral immunization with killed Haemophilus ztijluenzue for protection against acute bronchitis in chronic obstructive lung discase. Lancet 1985; ii: 1395-7. 9. Medical Research Council. Definition and classification of chronic hronchitis for clinical and epidemiological purposes. Lancet 1965; i: 775-9. 10. Adena MA, Wilson SR. Generalized linear models in epidemiological research case-control studies. INSTAT Foundation, Sydney, 1982. Aust N Z J Med 1991; 21
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11. Rice WR. A new probability model for determining exact pvalues for 2 x 2 contingency tables when comparing binomial proportions. Biometrics 1988; 44: 1-14. 12. Butt HL, Clancy RL, Cripps AW, Murree-Allen K, Saunders NA, Sutherland DC, Hensley MJ. Bacterial colonisation of the respiratory tract in chronic bronchitis. Aust NZ J Med (1990; 20: 35-8. 13. Wallace FJ, Clancy RL, Cripps AW. An animal model demon-
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stration of enhanced clearance of nontypable Haemophilus injhenzae from the respiratory tract after antigen stimulation of gut-associated lymphoid tissue. Am Rev Resp Dis 1989; 140: 311-6. 14. Mestecky J, McGhee JR, Arnold RR, Michaelek SM, Prince SJ, Babb JL. Selective induction of an immune response in human external secretions by ingestion of bacterial antigen. J Clin Invest 1978; 61: 731-7.
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