Evaluating the effectiveness of the universal immunization program against varicella in Japanese children
Fumihiko Hattori1, Hiroki Miura1, Ken Sugata1
1Department of Pediatrics, Fujita Health University School of Medicine, Toyoake, Aichi 470-1192, Japan.
Insights
The Oka/Biken varicella vaccine showed 76.9% effectiveness with one dose and 94.7% with two doses. Two doses are recommended for effective varicella control in Japan.
Area of Science:
- Immunology
- Virology
- Public Health
Background:
- The Oka/Biken vaccine was implemented in Japan's universal immunization program.
- Varicella (chickenpox) remains a concern despite vaccination efforts.
Purpose of the Study:
- To evaluate the effectiveness of the Oka/Biken varicella vaccine.
- To determine the impact of one versus two doses on vaccine effectiveness (VE).
Main Methods:
- A matched case-control study was conducted.
- Laboratory-confirmed varicella cases and unvaccinated controls under 15 years were enrolled.
- Molecular diagnostic assays confirmed varicella cases; matched odds ratios calculated VE.
Main Results:
- Varicella-zoster virus DNA was detected in 81.3% of suspected cases.
- One dose of Oka/Biken vaccine showed 76.9% adjusted VE.
- Two doses of Oka/Biken vaccine demonstrated 94.7% adjusted VE.
Conclusions:
- One dose of the Oka/Biken varicella vaccine is insufficient for controlling varicella.
- Two doses of the Oka/Biken vaccine are significant for effective varicella control in Japan.
Objective:
Matched case control study was conducted to elucidate the effectiveness of the Oka/Biken vaccine immediately after implementation of the universal immunization program in Japan.
Methods:
Cases were laboratory confirmed varicella patient under 15years of age diagnosed at 14 designated pediatric clinics between September 2015 and September 2016. Controls were selected from patients who visited the same practice for different reasons as the varicella case within 2weeks. Swab samples were collected from varicella suspected patients and molecular diagnostic assays were used to confirm varicella cases. Matched odds ratio were used to calculate vaccine effectiveness (VE).
Results:
Varicella zoster virus DNA was detected in 183 (81.3%) of 225 suspected cases. One sample was excluded because it was positive for the Oka vaccine strain (182/225, 80.9%). Three hundred twenty-three control subjects were enrolled. The effectiveness of 1 dose of the Oka/Biken vaccine compared with no vaccine was 76.7% (95% confidence interval [CI]: 58.6-86.9%; P<0.001). The effectiveness of 2 doses of the Oka/Biken vaccine was 94.2% (95% CI: 85.7-97.6%; P<0.001). After adjusting for potential confounding effects, the adjusted VE of 1 and 2 doses of varicella vaccine were 76.9% (95% CI: 58.1-87.3%; P<0.001) and 94.7% (95% CI: 86.0-98.0%; P<0.001), respectively.
Conclusions:
VE of one dose of Oka/Biken varicella vaccine was insufficient to control varicella. Therefore, two doses of Oka/Biken varicella vaccine is significant for controlling varicella in Japan.
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