Haemophilus influenzae oral vaccination for preventing acute exacerbations of chronic bronchitis and chronic obstructive pulmonary disease


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Review question

We reviewed the evidence about the effect of a non-typeable Haemophilus influenzae (NTHi) vaccine in preventing repeated H influenzae infections in people with chronic obstructive pulmonary disease (COPD) or chronic bronchitis.

Background

People with COPD can have frequent infections that worsen symptoms of their lung disease, that is increased breathlessness, purulent discharge and decompensating oxygen saturations levels, known as an ‘acute exacerbation’. The bacteria that most commonly causes this is H influenzae. Infection with H influenzae can lead to hospitalisation, and in some cases, death. Preventing these infections with a vaccine could lead to people with COPD having improved outcomes compared to the current practice of treating infections as they arise.

Study characteristics

The evidence is current to January 2017. We identified six studies with a total of 557 participants. The studies were blinded, placebo-controlled randomised trials that tested how effective the NTHi vaccine is in preventing infections in people over 18 years of age with COPD or chronic bronchitis. In all six trials, both the vaccine and placebo group were given at least three courses of tablets at regular intervals over a period of three to 12 months. Generally, the baseline demographics of participants across the included studies shared similar characteristics (such as diet, lifestyle, and living conditions) to other high-income countries. Ages ranged between 40 and 80 years. The studies counted the number of infections the participants experienced, levels of respiratory tract bacteria, deaths, side effects, hospital admissions, or treatment with antibiotics.

Key results

The NTHi vaccine had no significant impact on reducing the number of acute exacerbations experienced by people with COPD. There was no significant difference in mortality rate between the vaccine and placebo groups, and the reported deaths in the vaccinated group were not attributed to the vaccine.

The levels of H influenzae bacteria found in the respiratory tracts of participants did not differ between the vaccine and placebo groups. Due to inconsistencies of measurement between the trials, we were not able to compare the studies against one another.

Antibiotics, which can be an indicator of severe infection, were significantly more commonly prescribed in the placebo group. Evidence of hospital admissions showed that there was no difference in the likelihood of being hospitalised in either the vaccine or the placebo group. Two trials studying quality of life found that vaccinated participants generally had a better quality of life, but these results were measured differently and so could not be compared.

Five trials reported adverse effects, but there was no particular association with either the vaccine or placebo group. Further research is needed to define adverse effects as outcome measures for more definitive analyses regarding vaccine side effects.

Quality of the evidence

The studies were well conducted with moderate risk of bias. The main limitation of this review was the lack of consistency regarding the definitions and outcome measures among the individual studies, which affected the overall synthesis and interpretation of the results. Fewer participants may mean the results are more likely to be affected by chance. One trial had more participants than the other five trials combined, and it contributed more to the final analysis. There was moderate heterogeneity (the studies showed quite different results) when this study was included in the analysis, especially in numbers of infections. However, the results were consistent and did not change when this study was removed from the analysis.

Conclusion

We concluded after reviewing the relevant studies that the H influenzae vaccine taken orally in people with chronic bronchitis and COPD does not have a significant reduction in the number and severity of acute exacerbations.