Timeliness of Pediatric Influenza Vaccination Compared to Seasonal Influenza Activity In An Urban Underserved Community, 2004-2008

Background: Timely influenza vaccination of children is important given the variable onset of influenza activity each year, limited protection conferred by the prior season’s vaccine, and need for two doses in some children for optimal efficacy. Few, if any, studies have examined timeliness of pediatric influenza immunization compared to seasonal influenza activity. 

Objectives: To assess the temporal relationship between pediatric influenza vaccination and community influenza activity during the 2004-2008 seasons. 

Methods: In this retrospective cohort study, influenza vaccination was examined in 34,489 children from an urban underserved community using hospital and city immunization registries. Five cohorts included children ages 6 months-18 years in the 2004-5 through 2008-9 seasons. Cumulative proportions of those with any (≥1 dose) or full (i.e., 1-2 doses depending on requirements) coverage were calculated for each week during the five seasons. Community influenza activity, defined as the proportion of laboratory-confirmed influenza specimens, was determined weekly from New York State Department of Health reports. Coverage at the onset and peak of influenza activity and by March 31 was examined. Pearson’s correlation analyses assessed trends over time. Multivariable analyses determined the impact of age, race/ethnicity, language, and insurance on vaccine timeliness during the 2008-9 season.  

Results: Children were primarily Latino (52%), Spanish-speaking (42%), and publicly insured (84%). Few children had full coverage by the onset of influenza activity (4-20%), peak of influenza activity (8-39%), or by March 31 (11-43%) of each season, although coverage increased at the latter two time points over the five seasons. Multivariable analyses revealed that older, Latino, and Black children were less likely to have coverage at these time points.

Conclusions: Despite improvements in influenza vaccine timeliness, most children remained inadequately protected when influenza began circulating in the community. Determinants of influenza vaccine timeliness in children should be examined further.