Background: The pneumococcal conjugate vaccine (PCV) might prevent hospitalizations in children because of the role of Streptococcus pneumoniae in the complications of influenza infection. We investigated the benefit of PCV vaccination in preventing influenza hospitalization in children <5 years of age during the 2009 to 2010 pandemic wave and the 2010 to 2011 influenza epidemic in Spain.
Methods: A multicenter matched case-control study was undertaken in 27 hospitals from 7 Spanish regions between July 2009 and April 2011. A case was defined as a hospitalized patient between 6 months and 5 years of age with influenza virus infection confirmed by real-time reverse-transcription polymerase chain reaction. We selected 2 matched controls for each case from patients with unplanned hospital admission for reasons other than acute respiratory infection or influenza-like illness. Cases and controls were matched according to age, date of hospitalization and province of residence. Crude and adjusted odds ratios were calculated for associations between influenza hospitalization and PCV vaccination.
Results: One hundred ninety-four cases and 342 controls were included in the study. In the 2009 to 2010 pandemic wave, the adjusted benefit in preventing hospitalization was 48% (95% confidence interval: 1 to 76) in fully vaccinated children compared with -79% (95% confidence interval: -341 to 27) in the 2010 to 2011 influenza season.
Conclusions: The results obtained suggest that, in children <5 years of age, PCV vaccination reduced hospitalization during the 2009 to 2010 pandemic wave. By contrast, there was no observed benefit of vaccination in the 2010 to 2011 influenza season.