Thanks to Greg Folkers for sending the link to this report in The Journal of Infectious Diseases: Effectiveness of influenza vaccine against life-threatening RT-PCR-confirmed influenza illness in US children, 2010-2012. The abstract:
Background. No studies have examined the effectiveness of influenza vaccine against ICU admission associated with influenza virus infection among children.
Methods. In 2010-11 and 2011-12, children aged 6 months to 17 years admitted to 21 US pediatric intensive care units (PICUs) with acute severe respiratory illness and testing positive for influenza were enrolled as cases; children who tested negative were PICU controls. Community controls were children without an influenza-related hospitalization, matched to cases by comorbidities and geographic region. Vaccine effectiveness was estimated with logistic regression models.
Results. We analyzed data from 44 cases, 172 PICU controls, and 93 community controls. Eighteen percent of cases, 31% of PICU controls, and 51% of community controls were fully vaccinated. Compared to unvaccinated children, children who were fully vaccinated were 74% (95% CI, 19 to 91%) or 82% (95% CI, 23 to 96%) less likely to be admitted to a PICU for influenza compared to PICU controls or community controls, respectively. Receipt of one dose of vaccine among children for whom two doses were recommended was not protective.
Conclusion. During the 2010-11 and 2011-12 US influenza seasons, influenza vaccination was associated with a three-quarters reduction in the risk of life-threatening influenza illness in children.