Most of the children and adolescents who died from influenza in the United States between 2010 and 2014 were unvaccinated, a new case cohort analysis has found.
"Among deaths in children with known vaccination status, children who died had lower vaccination uptake for all age categories, seasons, and infecting influenza virus types than the [National Immunization Survey–Flu (NIS-Flu)] cohort," the researchers write.
Brendan Flannery, PhD, from the Influenza Division and Immunization Services Division at the Centers for Disease Control and Prevention in Atlanta, Georgia, and colleagues report their findings in an article published online April 3 in Pediatrics.
The study included deaths in US residents younger than 18 years who had laboratory-confirmed influenza virus infection reported to the Influenza-Associated Pediatric Mortality Surveillance System. The study included children who were aged at least 6 months on November 1 of the influenza season during which the child died, who were eligible to receive at least one dose of seasonal influenza vaccine, and for whom a complete medical history was available.
The investigators used three comparison cohorts: NIS-Flu, the National Health Interview Survey, and the MarketScan Commercial Claims and Encounters database.
During the study period, vaccination status was determined for 291 of 358 laboratory-confirmed influenza-associated pediatric deaths. Of those, 75 (26%) received seasonal influenza vaccination at least 14 days before they became ill. Vaccine type was known for 62 cases: 12 (19%) children received live-attenuated influenza vaccine and 50 (81%) received inactivated influenza vaccines.
In contrast, overall vaccination coverage was 48% among the NIS-Flu cohorts.
The researchers estimate that vaccine effectiveness against pediatric death was 65% (95% confidence interval [CI], 54% - 74%).
Vaccine effectiveness ranged from 54% during the 2010 to 2011 season to 80% during the mild 2011 to 2012 season, when the number of pediatric deaths was the lowest.
Vaccine effectiveness point estimates against death associated with influenza A virus (66%) and influenza B virus (62%) were similar.
The authors note that 53% of the deaths in children with known vaccination status occurred among those with one or more underlying high-risk medical conditions. Of those, 47 (31%) were vaccinated.
The researchers did find that children with one or more high-risk conditions were more likely to be vaccinated than their peers without such conditions. Specifically, the vaccination rate was 20% among children without high-risk conditions, 31% among children with one or more high-risk condition, and 37% among children with two or more high-risk conditions. Overall, however, less than half of all individuals in high-risk categories were vaccinated, the researchers note.
"Results of this study suggest that vaccination reduced the risk of influenza-associated death among children and adolescents and add to the evidence of benefits of influenza vaccination for children," the researchers conclude. "Annual vaccination is an important strategy to prevent influenza and influenza-associated complications and deaths. These results support current recommendations for annual influenza vaccination for all children ≥6 months of age."
The authors have disclosed no relevant financial relationships.
Pediatrics. Published online April 3, 2017. Article abstract
Medscape Medical News © 2017
Cite this: Pediatric Influenza Deaths Concentrated in Unvaccinated Kids - Medscape - Apr 03, 2017.