PHILADELPHIA, PA—Revaccination of children with live-attenuated influenza vaccine (LAIV) over 2 consecutive seasons did not reduce vaccine efficacy, and was similar to, or higher than, efficacy of a single LAIV administration in the second season, reported Herve Caspard, MD, from AstraZeneca, Gaithersburg, MD, at IDWeek 2014.
Dr. Caspard and colleagues conducted a meta-analysis of all 4 published, randomized double-blind clinical trials that evaluated the efficacy of LAIV vs. placebo against laboratory confirmed cases of influenza, in children across 2 consecutive influenza seasons. LAIV was administered as 2 doses in season 1 and as 1 dose in season 2, and consisted of 106.5–7.5 median tissue culture infectious doses of each of the 3 influenza strains: A/H1N1, A/H3N2, and B.
A total of 6,090 children, aged 18 months–7 years in season 2 were included. When administered over 2 seasons, LAIV efficacy in season 2 was 76.6% (95% CI 66.3%, 83.7%) against all strains and 86.7% (95% CI 76.8%, 92.4%) against antigenically similar strains.
Without revaccination, residual efficacy in season 2 of LAIV administered in the prior season was 40.7% (22.6%, 54.6%) against all influenza strains and 56.4% (37.0%, 69.8%) against antigenically similar strains. The additional efficacy of LAIV administered in season 2 was 27.6% (0.8%, 47.2%) against all strains and 58.4% (28.3%, 75.9%) against antigenically similar strains.
“LAIV administered over 2 consecutive seasons was equally efficacious compared with LAIV administered in season 2 only,” reported Dr. Caspard. Relative efficacy was -3.2% (-49.1%, 28.5%) against all strains, and 53.9% (17.4%, 74.3%) against antigenically similar strains, where administration over 2 consecutive seasons was more efficacious than administration in season 2 only.