Epidemiological Impact of the Pediatric Live Attenuated Influenza Vaccine (LAIV) Program on Group A Streptococcus (GAS) Infection in England

Background. Influenza is known to predispose to secondary bacterial infections including invasive group A streptococcal (iGAS) disease. The universal pediatric live attenuated influenza vaccine (LAIV) program introduced in England from the 2013/ 2014 influenza season was implemented incrementally, introducing cohorts of children annually to 2–16 years of coverage. Additionally, from the beginning of the program, discrete pilot areas offered LAIV vaccination to all primary school–age children, allowing for a unique comparison of infection rates between pilot and nonpilot areas during the program rollout. Methods. Cumulative incidence rate ratios (IRRs) of GAS infections (all), scarlet fever (SF), and iGAS infection within each season by age group were compared for pilot and nonpilot areas using Poisson regression. The overall effect of the pilot program in the pre- (2010/2011–2012/2013 seasons) and postintroduction (2013/2014–2016/2017 seasons) periods was assessed using negative binomial regression by comparing changes in incidence between pilot/nonpilot areas (ratio of IRR [rIRR]). Results. Reductions in IRRs of GAS and SF were observed within most post-LAIV program seasons, among the age groups 2–4 and 5–10 years. Significant reductions were seen among 5–10 years (rIRR, 0.57; 95% CI, 0.45–0.71; P < .001), 2–4 years (rIRR, 0.62; 95% CI, 0.43–0.90; P = .011), and 11–16 years (rIRR, 0.63; 95% CI, 0.43–0.90; P = .018) for GAS infections when assessing the overall effect of the program. Conclusions. Our findings suggest that vaccination with LAIV may be associated with a reduced risk of GAS infection and support attaining high uptake of childhood influenza vaccination.