Updated estimation of the impact of a Japanese encephalitis immunization program with live, attenuated SA 14-14-2 vaccine in Nepal

Abstract

BackgroundJapanese encephalitis (JE) is a mosquito-borne disease that is associated with considerable morbidity and mortality in many Asian countries. The objective of this study was to describe the impact of the JE immunization program using SA 14-14-2 JE vaccine implemented in Nepal during 2006 through 2011. A previous assessment after the initial program implementation phase described a significantly lower post-campaign JE incidence compared to expected incidence; however, the previous evaluation had limited post-campaign data for some districts.Methodology/Principal findingsJE and acute encephalitis syndrome (AES) data gathered through Nepal’s routine surveillance system from 2004 through 2014 were analyzed to assess the impact of the JE immunization program implemented in 31 districts. Expected incidence rates were determined by calculating the incidence of cases per 100,000 person-years in each district before the vaccination campaigns. This rate was applied to the relevant population after the vaccination campaigns, which provided the expected number of cases had the campaign not occurred. The observed incidence rate was the number of reported cases per 100,000 person-years post-campaign. Expected and observed JE and AES cases and incidence rates were compared. The post-campaign JE incidence rate of 0.7 cases per 100,000 was 78% (95% CI 76%–79%) lower than expected had no campaign occurred and an estimated 3,011 (95% CI 2,941–3,057) JE cases were prevented. The post-vaccination AES incidence of 5.5 cases per 100,000 was 59% (58%–60%) lower than the expected and an estimated 9,497 (95% CI 9,268–9,584) AES cases were prevented.Conclusions/SignificanceThis analysis strengthens previous findings of the substantial impact of Nepal’s JE immunization program using SA 14-14-2 JE vaccine.

Microneedle‐based intradermal delivery of stabilized dengue virus

“…[8][9][10][11][12] Like other successful flavivirus vaccines against yellow fever and Japanese encephalitis, the majority of dengue vaccine candidates either approved for limited license or in Phase III trials are LAVs. 8,[13][14][15] These require shipment in lyophilized form at 4 C and must be reconstituted immediately before use to avoid loss in potency. 16,17 Therefore, systems enabling the preservation of DENV viability in dry formulation and at ambient temperatures will be essential for the development of LAVs that can be delivered and administered under CTC conditions.…”

“…This is partly due to the complexity of dengue epidemiology, population immunity, and the interplay between viral pathogenesis and host immunological mechanisms . Like other successful flavivirus vaccines against yellow fever and Japanese encephalitis, the majority of dengue vaccine candidates either approved for limited license or in Phase III trials are LAVs . These require shipment in lyophilized form at 4 °C and must be reconstituted immediately before use to avoid loss in potency .…”

Hospital-based surveillance for Japanese encephalitis in Bangladesh, 2007–2016: Implications for introduction of immunization

“…However, in the context of limited evidence regarding the effectiveness of vector control, bed nets, swine immunization or animal sequestration ( Igarashi, 2002 ), WHO recommends that countries achieve and maintain high human vaccine coverage to realize the greatest reductions in the number of human JE cases ( WHO, 2016 ). Studies conducted in other JE-endemic Asian countries have reported human immunization is effective in terms of decreasing AMES burden and health care costs ( Touch et al, 2010 , Upreti et al, 2017 , Yin et al, 2012 ). Immunization strategies including but not limited to introduction of JE vaccine into the routine childhood immunization program, mass vaccination of children under 15 years of age, and mass vaccination in limited geographic areas need to be examined, considering the cost-effectiveness ratio of the approach and potential for substantially decreasing disease burden.…”

Development and validation of an assay for detection of Japanese encephalitis virus specific antibody responses

“…Although pre-existent JEV antibodies due to JEV vaccination has shown to potentiate DENV infection in vitro and although our data suggest that those who had received the JEV vaccine (and therefore had JEV-specific IgG antibodies) were more likely to have severe dengue, these data should be further validated by carrying out careful prospective studies in the communities where these viruses co-circulate. Given that the JEV vaccine has significantly reduced mortality and morbidity of encephalitis due to JEV throughout the world including Sri Lanka [ 27 , 32 , 33 ], it would be important to carefully examine such associations in other JEV and DENV endemic countries before concluding that JEV increases dengue disease severity.…”