A Cochrane review included 6 studies with a total of 919 subjects. There was no evidence that pneumococcal vaccination during pregnancy reduces the risk of neonatal infection (relative risk (RR) 0.66; 95% confidence interval (CI) 0.30 to 1.46; 2 trials, 241 pregnancies). Although the data suggest an effect in reducing pneumococcal colonisation in infants by 16 months of age (one trial, 56 pregnancies, RR 0.33; 95% CI 0.11 to 0.98), there was no evidence of this effect in infants at two or three months of age (average RR 1.13; 95% CI 0.46 to 2.78; 2 trials, n=146, low quality evidence) or by six or seven months of age (average RR 0.67, 95% CI 0.22 to 2.08; n=148, low quality evidence).
Comment: The quality of evidence is downgraded by study quality (inadequate or unclear allocation concealment), by imprecise results (few patients and outcome events), and by indirectness (e.g., neonatal infection, the most significant outcome, was reported in only 2 trials).