Summary of meta-analyses for immune response to vaccination.

* = some studies contributed two sets of data included in this meta-analysis; (S) = seasonal; (P) = pandemic; ES = effect size; CI = confidence interval; SC1 = seroconversion (≥4 fold rise post vaccination); SC2 = seroconversion (<1∶40 to ≥1∶40 haemagglutination inhibition titre); SP = seroprotection (≥1∶40 haemagglutination inhibition titre post vaccination); VICT = vaccinated immunocompetent controls; PNV = placebo or no vaccination; NS = not statistically significant. See Figure S2 for citation details.