Correlates of Immune Protection Induced by Live, Attenuated, Cold‐Adapted, Trivalent, Intranasal Influenza Virus Vaccine

TLDR

The study aimed to evaluate the efficacy of a live attenuated influenza vaccine and identify immune correlates of protection against experimental H1N1 challenge in children. A 2‑year, multicenter, double‑blind, placebo‑controlled field trial was conducted, with pre‑challenge serum HAI and nasal wash IgA measurements, and children were challenged intranasally with 107 TCID50 of attenuated H1N1. The vaccine was 92 % efficacious against H3N2/B and 83 % against H1N1, with any serum HAI or nasal IgA antibody correlating with significant protection from H1N1 shedding.

Abstract

The authors conducted a 2-year, multicenter, double-blind, placebo-controlled efficacy field trial of live, attenuated, cold-adapted, trivalent influenza vaccine administered by nasal spray to children 15–71 months old. Overall, vaccine was 92% efficacious at preventing culture-confirmed infection by influenza A/H3N2 and influenza B. Because influenza A/H1N1 did not cause disease during the years in which this study was conducted, the authors sought to determine vaccine efficacy and correlates of immune protection against experimental challenge with 107 TCID50 of attenuated H1N1 (vaccine strain) by intranasal spray. Prechallenge assessments included serum hemaglutination-inhibiting (HAI) antibody and nasal wash IgA antibody to H1N1. Vaccine was 83% efficacious (95% confidence interval, 60%–93%) at preventing shedding of H1N1 virus after challenge. Any serum HAI antibody or any nasal wash IgA antibody was correlated with significant protection from H1N1 infection as indicated by vaccine-virus shedding, and high efficacy against H1N1 challenge was demonstrated.