Effectiveness of rotavirus vaccines against hospitalisations in Japan

Abstract

BackgroundIn Japan, rotavirus hospitalisation occurs at a rate from 2.8 to 13.7 per 1000 child-years among children age less than 5 years, and it imposes a substantial burden to the healthcare system in the country. While both monovalent (RV1) and pentavalent (RV5) rotavirus vaccines are licensed in Japan, neither has been incorporated in the national infant immunization programme. In this study, we estimated vaccine effectiveness (VE) in Japan.MethodsThis study was conducted in Yuri-Kumiai General Hospital located in a city in the north-western part of Japan. Age-eligible children for rotavirus vaccination were enrolled if they were hospitalized for rotavirus gastroenteritis between September 2013 and August 2016. Rotavirus gastroenteritis was defined by the detection of rotavirus antigen by immunochromatography. “Vaccinated” was defined as infant inoculated with at least one dose of either RV1 or RV5. A conditional logistic regression analysis was performed by modelling the year of birth, year of admission, residence of the children and vaccination status, and by matching the age of cases with that of test-negative controls. The adjusted odds ratio of the vaccinated over unvaccinated was then used to calculate VE in the formula of (1 – adjusted odds ratio) × 100.ResultsOut of the 244 patients enrolled, rotavirus antigen was detected in 55 (22.5%) of whom 10 (18.2%) were vaccinated, whereas 94 (49.7%) of 189 test-negative controls were vaccinated. During the study period, the vaccine uptake rate in the controls increased from 36.2% to 61.8%. On the other hand, the vaccination coverage over the three years was 64.2% in Yuri-Honjo city (three quarters of the catchment), and 91.4% in Nikaho city (one quarter of the catchment). The VE was calculated to be 70.4% (95% confidence interval: 36.0–86.4%, P = 0.002). The point estimate of the VE was lower but its 95% confidence interval overlaps those of the efficacies obtained from clinical trials in Japan.ConclusionThe rotavirus vaccine was effective in the real-world setting in Japan as in the clinical trials, and the introduction of rotavirus vaccine in the national infant immunization schedule will substantially reduce the number of rotavirus gastroenteritis hospitalisation in Japan.

Case-Control Study of Rotavirus Vaccine Effectiveness Compared to Test-Negative Controls or Hospital Controls

“…The VE against severe RVGE requiring hospitalization was calculated as 70.4% in that study. 19 The estimate of VE (86.6% [95% CI, 55.9–96.0]) in our present study was higher than previous studies in Japan, although the confidence interval overlaps those of previous studies, as well as those from other developed countries. 20 – 22…”

“…To date, to the best of our knowledge, there are only two studies that evaluated rotavirus vaccine effectiveness in Japan. 18 , 19 One is our own previous case-population study in Saga Prefecture, which reported a 69.5% VE against RVGE and 88.8% VE against severe RVGE requiring hospitalization. 18 That study was important for monitoring VE; it was the first on VE undertaken shortly after introduction of the rotavirus vaccines.…”

Effectiveness of monovalent rotavirus vaccine in the Philippines

“…In Asia, few countries have introduced RVV. Earlier results from high income countries of Asia in Hong Kong 7 and Japan 8 , where RVV are self-financed, revealed RVV effectiveness of 89% and 70%, respectively against diarrheal hospitalization. However, a cluster-randomized study conducted in Bangladesh, a low income country, revealed that the monovalent RVV effectiveness was 41.4% 9 .…”

A review of rotavirus vaccine use in Asia and the Pacific regions: challenges and future prospects

“…Three studies from China reported vaccine effectiveness estimates ranging between 35%-44.6% against RVGE cases [32][33][34] and one study reported vaccine effectiveness of 74.5% against RVGE hospitalization [33]. Data from Japan reported vaccine effectiveness estimates ranging from 70.4%-97.3% against RVGE requiring hospitalization [35][36][37]. A study from Australia, reported a vaccine effectiveness of 84.5% against RVGE hospitalization [38].…”