Safety and immunogenicity of live-attenuated Japanese encephalitis SA 14-14-2 vaccine co-administered with measles vaccine in 9-month-old infants in Sri Lanka

AbstractIntroductionTo facilitate introduction of live attenuated SA 14-14-2 Japanese encephalitis vaccine (LJEV) into the National Immunization Programme of Sri Lanka, we evaluated the safety and immunogenicity of co-administration of LJEV and measles vaccine at 9 months of age. Serum immune responses were evaluated post-vaccination on days 28, 180, and 365 using JE neutralization test and anti-measles IgG ELISA.Results278 infants received one dose of LJEV and measles vaccine. Of these, 257 were eligible for the per-protocol analysis. On Day 0, 14 infants (5.5%) were seropositive for JE, but none were seropositive for measles. At Day 28, seropositivity rates were 90.7% (95% CI, 86.4–93.9%) for JE and 84.8% (95% CI, 79.8–89.0%) for measles. The geometric mean titer for JE neutralizing antibodies was 111 (95% CI, 90–135), and the geometric mean concentration (GMC) for anti-measles IgG was 375mIU/mL (95% CI, 351–400mIU/mL). Over the next year, JE neutralizing antibody responses declined only slightly, with seropositivity at 87.4% (95% CI, 82.6–91.2%) at Day 365. In contrast, measles antibody levels continued to increase over time. Seropositivity for anti-measles IgG reached 97.2% (95% CI, 94.4–98.9%) at Day 365, and the GMC rose to 1202mIU/mL (95% CI, 1077–1341mIU/mL). Co-administration of LJEV and measles vaccine was also safe. Most adverse reactions were mild, and no serious adverse events were related to study vaccinations.ConclusionThe safety and immunogenicity of LJEV co-administered with measles vaccine in Sri Lankan infants is similar to that seen in other populations, and our results support use of LJEV at 9 months of age. Live SA 14-14-2 vaccine is now prequalified by the WHO for use in infants in Asia, and other countries may wish to introduce LJEV to combat this devastating disease