Impact of different case definitions for acute otitis media on the efficacy estimates of a pneumococcal conjugate vaccine.

Considerably higher vaccine efficacy estimate for clinical acute otitis media (AOM) has been obtained for the 11-valent pneumococcal conjugate vaccine with protein D of Haemophilus influenzae as a carrier (PncPD11) in the POET study than for the 7-valent pneumococcal conjugate vaccine (PncCRM7) in the Finnish Otitis Media (FinOM) Vaccine Trial. We recalculated PncCRM7 efficacy from the FinOM data using a case definition for AOM very close to the POET definition and a definition giving an incidence for AOM in the control group comparable to that obtained in the POET study. The different case definitions had only a slight impact on the vaccine efficacy estimates compared to the original case definitions. We were not able to show that the differences between the study results would be due to the case definitions used.