Immunogenicity & safety of a single dose of live-attenuated Japanese encephalitis vaccine SA 14-14-2 in adults

Abstract

Background & objectives:Japanese encephalitis (JE) caused by mosquito-borne Flavivirus is one of the leading causes of viral encephalitis in Asia. Control strategies include vector control and human vaccination. Due to lack of immunization programmes in endemic regions, there are still high mortality and morbidity. A live-attenuated SA 14-14-2 JE vaccine (LAJEV) has been licensed and used in Asian countries, including India. We report the assessment of immunogenicity and safety of the vaccine in adults during the first mass adult vaccination campaign carried out in Assam, India.Methods:One thousand and seventy five adults (aged ≥15 yr) who received LAJEV were monitored for adverse events following immunization for one year. The safety assessment of vaccinated population was evaluated till 28 days and at 6 and 12 months. Blood samples collected from the enrolled participants were tested by plaque reduction neutralization test (PRNT50) to assess the neutralizing antibody titres (NATs) before vaccination and 28 days, six and 12 months post-vaccination (PV).Results:Among the 1075 vaccinated individuals, four reported minor adverse effects from 30 min to 28 days PV. Based on the pre-vaccination NAT, the study participants were categorized as seronegative, moderately seropositive and strongly seropositive. Nearly 85.5 per cent of JE seronegative participants seroconverted by 28 days PV. The geometric mean titre (GMT) in all the three groups increased by 28 days and decreased by six and 12 months PV. Nearly 60 per cent of the moderately positive individuals exhibited four-fold rise in GMT, 28 days PV. Almost 95.5 per cent of the participants in the study population remained seroprotected at the end of 12 months PV.Interpretation & conclusions:This study on immunogenicity and safety of LAJEV in adults showed that a single dose of the live-attenuated vaccine was safe and induced protective immunity to both JE seronegative and naturally seropositive adults. Further study is required to find out long term protective efficacy of this vaccine.

CD8+ T cells are crucial for humoral immunity establishment by SA14‐14‐2 live attenuated Japanese encephalitis vaccine in mice

“…The SA14‐14‐2 vaccine is a widely used vaccine included in national immunization programs of several JE‐affected countries [2]. A single dose of SA14‐14‐2 JE vaccine elicits excellent immunogenicity and results in 85–94.5% seroconversion 28 days postvaccination among seronegative individuals [3–5]. Although more than 90% efficacy has been reported at 1‐year postvaccination [6,7], the long‐term efficacy of live‐attenuated SA14‐14‐2 vaccine varies depending on the age group and the demography.…”

Use of the live attenuated Japanese Encephalitis vaccine SA 14–14–2 in children: A review of safety and tolerability studies

“…A recent study reported that a single dose of LAJEV also can be safely administered to adults, generating immunity among both seronegative and naturally seropositive adults. 38 Furthermore, data on the co-administration of LAJEV with MV shows an acceptable short-term safety profile, 15 which may encourage endemic JE countries to revise their national immunization programs to reflect a co-administration of the 2 vaccines as in Sri Lanka. 39 An immunogenicity study examining the co-administration of LAJEV and MV just completed in China, 40 and an immunogenicity and safety study is underway in the Philippines to evaluate the co-administration of LAJEV and the measles-mumpsrubella (MMR) vaccine which pending the results, may turn into an official recommendation for interested countries.…”

Safety of Japanese encephalitis vaccines

“… 36 , 40 , 41 Another study on immunogenicity and safety of live attenuated SA14-14-2 JE vaccine in India showed that a single dose induced protective immunity in both JE seronegative and naturally seropositive adults. 42 Almost 95.5% of the participants remained seroprotected at the end of 12-month follow-up. 42 A 30-day follow-up study of live-attenuated SA14-14-2 JE vaccine in 26,239 children showed that the incidence of encephalitis, meningitis, all-cause hospitalization or other serious adverse events was no higher than the control group.…”

“… 42 Almost 95.5% of the participants remained seroprotected at the end of 12-month follow-up. 42 A 30-day follow-up study of live-attenuated SA14-14-2 JE vaccine in 26,239 children showed that the incidence of encephalitis, meningitis, all-cause hospitalization or other serious adverse events was no higher than the control group. 43 The risk ratios of all-cause hospitalization were 0.70 (95% confidence interval 0.43–1.15), and fever was 0.79 (95% confidence interval 0.56–1.11).…”