A Cochrane review (abstract , review ) [withdrawn from publication] included 6 studies with a total of 257 000 infants. Four of the studies were included in the meta-analyses. The relative risk of invasive Hib disease (meningitis, pneumonia, bacteraemia, cellulitis, epiglottitis, arthritis) was 0.20 (95% CI 0.07 to 0.54), but there was statistically significant unexplained heterogeneity. The size of the effects did not appear to differ consistently with different vaccine types, the number of vaccine doses, age at first vaccination or use in high income versus low income countries, but the CIs for the effect estimates were wide. Hib-related mortality data showed a non-significant trend towards benefit (relative risk 0.29, 95% CI 0.07 to 1.20). The relative risk for all cause mortality in the two trials from which data were available were 1.01 (95% CI 0.38 to 2.67, random-effects model) and 0.97. No serious adverse events were reported in any of the trials.