A meta-analysis of case-control studies supports the use of the 13-valent pneumococcal conjugate vaccine (PCV13) in children because it provides protection against serotype 3 invasive pneumococcal disease, according to study results published in Clinical Infectious Diseases.

There was no prelicensure efficacy trial for the PCV13 vaccine, and therefore estimates of its effectiveness against additional serotypes have been obtained from postlicensure observational studies. These studies have shown inconsistent results, leading to the conclusion by some authors of modeling studies that PCV13 does not protect against serotype 3 invasive pneumococcal disease. In this study, researchers conducted a systematic literature review and meta-analysis to evaluate the effectiveness of this vaccine against serotype 3 invasive pneumococcal disease in infants and children age <5 years.

A total of 6 publications of 403 reviewed articles were included in the analysis (4 published studies and 2 conference posters) that provided PCV13 effectiveness estimates stratified by serotype. The 4 published studies were matched case-control or indirect cohort studies. The pooled PCV13 vaccine effectiveness against serotype 3 invasive pneumococcal disease from the random effects meta-analysis was 63.5% (95% CI, 37.3-89.7), and a sensitivity analysis showed an estimate of 72.4% vaccine effectiveness against serotype 3 (95% CI, 56.7-88.0; P =.891).

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The researchers noted that the study has limitations. For example, “statistical tests which are used to exclude the hypothesis of a heterogeneity of effect estimates in a meta-analysis (the null hypothesis being the absence of heterogeneity) are not sensitive when the number of studies under review is limited.” Another limitation was that observational studies are subject to substantial confounding from a variety of biases.

“This information will be critical for understanding the best public health use of the current vaccine and for developing better vaccines,” researchers concluded.

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Sings HL, De Wals P, Gessner BD, et al. Effectiveness of 13-valent pneumococcal conjugate vaccine against invasive disease caused by serotype 3 in children: a systematic review and meta-analysis of observational studies [published online October 23, 2018]. Clin Infect Dis. doi: 10.1093/cid/ciy920