Effectiveness versus efficacy of conjugated pneumococcal vaccine: a systematic review of randomised, controlled trials with meta-analysis examining absolute risk reduction and relative risk
You have free access to this content Clinical Microbiology and InfectionVolume 17, Issue Supplement s4, Article first published online: 4 MAY 2011 http://onlinelibrary.wiley.com/doi/10.1111/j.1469-0691.2011.03558.x/pdf Page 299 P1442
Effectiveness versus efficacy of conjugated pneumococcal vaccine: a systematic review of randomised, controlled trials with meta-analysis examining absolute risk reduction and relative risk
Objectives: Use of the 7-valent pneumococcal conjugate vaccine (PCV7) resulted in reduction in vaccine serotypes invasive pneumococcal disease (IPD). However, IPD due to serotypes not included in the PCV7 increased in frequency. This prompted the introduction of a 13 valent vaccine. Previous systematic reviews have examined vaccine efficacy (odds ratio and relative risk). However, effectiveness of PCV in reducing childhood morbidity and mortality (in terms of absolute risk reduction (ARR) and numbers needed to treat (NNT)) has not been published. At the threshold of introducing the PCV13, such an assessment of the old vaccine is useful for comparison. The objective here was to evaluate the effectiveness of PCV through a systematic review of literature.
Methods: Systematic literature search for randomized controlled trials reporting on measures of vaccine effectiveness (invasive Pneumococcal disease, pneumonia, meningitis, all-cause mortality, Pneumococcal disease specific mortality, and systemic adverse events/effects) was undertaken and data extracted based on a priori criteria. Data were analysed to calculate odds ratio, relative risk and absolute risk reduction (ARR); and pooled through meta-analysis. Number needed to treat (vaccinate) was calculated for effectiveness.
Results : There were five methodologically good trials presenting data through 11 publications. There was a small but statistically significant benefit of vaccination on clinical pneumonia (OR=0.927, 95%CI 0.885-0.971, NNT=200), radiological pneumonia (OR=0.749; 95%CI 0.682-0.822, NNT=143) and invasive disease caused by vaccine serotypes (OR=0.215, 95%CI 0.149-0.311, NNV=500). The effect on all-cause mortality was OR and RR=0.88, 95%CI 0.78 to 0.99, and RD 0.00, 95%CI -0.01 to 0.00 (NNT cannot be calculated). There was no difference in invasive Pneumococcal disease caused by vaccine-related and vaccine-unrelated serotypes. There was no data on meningitis and Pneumococcal disease-specific mortality. Examination of multiple adverse events did not show a difference in risk compared to control, except for a small but statistically significant increase in risk of asthma.
Conclusion: PCV7 appears to have limited effectiveness against pneumonia; but does not reduce all-cause mortality. There is significant reduction in vaccine serotype IPD. There is no data to draw conclusions for other clinical problems of public health significance such as meningitis, and Pneumococcal disease-specific mortality.