A Cochrane review [Abstract] 1 [withdrawn from the Cochrane library] included 6 studies with a total of 440 subjects with either chronic obstructive pulmonary disease (COPD) or recurrent acute exacerbations of chronic bronchitis. Oral monobacterial, whole-killed cell nontypeable Haemophilus influenzae vaccine reduced the incidence of bronchitic episodes at three months after vaccination (rate ratio is 0.69; 95% CI 0.41 to 1.14) and at six months after vaccination (rate ratio 0.82; 95% CI 0.62 to 1.09). If these results had been statistically significant, they would have represented a reduction in acute bronchitic attacks for vaccinated individuals of 31% at three months, and 18% at six. The effect had disappeared by nine months. The severity of exacerbations in the treatment group, as measured by requirement to prescribe antibiotics, was likewise reduced by 58% at three months (Peto odds ratio = 0.42; 95% CI 0.16 to 1.13), and by 65% at six months (Peto odds ratio = 0.35; 95% CI 0.16 to 0.75).
Comment: The quality of evidence is downgraded by imprecise results (few patients and wide confidence intervals) and by inconsistency (variability in results across studies).
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