The Efficacy of Live Attenuated and Inactivated Influenza Vaccines in Children as a Function of Time Postvaccination

For matched strains, data suggest that the relative efficacy of LAIV versus TIV in young children increases over time. Consistent with previous studies of TIV-induced immunity, this analysis suggests that the absolute efficacy of TIV against matched strains in children may be lower at >4 to 8 versus 0 to 4 months postvaccination. Relative efficacy against mismatched strains was similar over time, consistent with previous estimates of the absolute efficacies of the vaccines against mismatched strains. Further research is needed to confirm these findings and to characterize the duration of protection provided by TIV in children.