Effectiveness of Japanese encephalitis vaccination among children in central India

Abstract

Japanese encephalitis (JE) disease among children continues in central India despite vaccination implemented in the routine immunization program. Therefore, we planned to estimate the JE vaccination effectiveness among children by undertaking a 1:2 individually‐matched population‐based case‐control study from August 2018 to October 2020. The laboratory‐confirmed JE cases aged 1–15 years were enrolled along with neighborhood controls without fever and encephalitis matched on the residence area, age and sex. The JE vaccination history was enquired from parents and verified independently from the vaccination cards available at home and records at health facilities. We enrolled 35 JE cases and 70 matched controls. The vaccination effectiveness of 86.7% (95% confidence interval [CI]: 30.8–94.7) was estimated on the per‐protocol analysis of 31 case‐control sets. The screening method provided an effectiveness of 89.5% (CI: 78.9–94.7) on using the population vaccination coverage of 90% reported earlier in the same area. In conclusion, JE vaccination offered a moderate level of protection among children in JE medium‐endemic central India, similar to reports from high‐endemic areas in India. The operational aspects of vaccination program implementation need to be evaluated to assess the impact of vaccination on the disease burden of JE in medium‐endemic regions of India.

Epidemiology of Japanese Encephalitis in Central India after Implementing Immunization

“…Good coverage of JE vaccination was reported earlier 13 in Maharashtra (94.8%) and Telangana (92.8%), with a reasonable level of protection among children. 14 In Tamil Nadu, JE cases were reduced in vaccinated districts, while cases were higher in nonvaccinated districts. 15 After the JE vaccine introduction, the case fatality ratio reduced but the JE disease burden continued.…”

Adults in Northwest China experienced the largest outbreak of Japanese encephalitis in history 10 years after the Japanese encephalitis vaccine was included in the national immunization program: A retrospective epidemiological study

“…JE was first discovered in Japan in 1871 and has since spread to Southeast Asia and the Western Pacific 4,5 . It is estimated that approximately 68 000 JE cases occur worldwide annually, with a fatality rate ranging from 20% to 30% 6–8 . In the last century, JE was a serious public health problem in China, posing a serious threat to the health of the people 9 .…”

“…4,5 It is estimated that approximately 68 000 JE cases occur worldwide annually, with a fatality rate ranging from 20% to 30%. [6][7][8] In the last century, JE was a serious public health problem in China, posing a serious threat to the health of the people. 9 To control the epidemic of JE, China started to use the inactivated P3 vaccine (Beijing-P3 strain) in regions with a high prevalence of JE in 1968, and a total of five doses of this JE vaccine are required (two doses at 12 months, followed by one dose at 2, 6 and 10 years of age).…”