What is the clinical evidence from this study?

Study design: Observational. Population: Vaccine-associated paralytic poliomyelitis (VAPP) (n=33). Intervention: Oral poliovirus vaccine (OPV). Primary outcome: Overall risk of VAPP per million OPV doses administered (1 case per 2.0 million doses, 95% CI 1/2.9 million - 1/1.5 million).

March 28, 2008Japanese Journal of Infectious Diseases16 citationsOpen Access

Poisson-Model Analysis of the Risk of Vaccine-Associated Paralytic Poliomyelitis in Japan between 1971 and 2000

LHLixin Hao STSatoshi Toyokawa YKYasuki Kobayashi

Key Result

The overall risk of vaccine-associated paralytic poliomyelitis in Japan between 1971 and 2000 was one case per 2.0 million oral poliovirus vaccine doses administered.

Study Design

Type

Observational (n=33)

Structured PICO

What is the risk of vaccine-associated paralytic poliomyelitis following oral poliovirus vaccination in Japan?

Population

33 cases of vaccine-associated paralytic poliomyelitis were identified in Japan over a 30-year period out of 66.4 million oral poliovirus vaccine doses administered.

Exposure

Oral poliovirus vaccine (OPV)

Outcome

Risk of vaccine-associated paralytic poliomyelitis (VAPP)safety

The occurrence of vaccine-associated paralytic poliomyelitis is rare but remained constant at approximately one case per 2.0 million OPV doses in Japan between 1971 and 2000.

Main Result

Effect estimate: 1 case per 2.0 million doses (95% CI 1/2.9 million - 1/1.5 million)

Limitations

Reliance on only reported VAPP cases, which might have led to an underestimation of the true risk.
Assumption that annual doses of OPV administered were constant for the Runs test and Poisson model analyses, despite year-to-year variances.

Abstract

This study estimates the risk of vaccine-associated paralytic poliomyelitis (VAPP) in Japan between 1971 and 2000. We acquired data regarding the number of VAPP cases from the website of the Ministry of Health, Labour and Welfare, and we estimated the number of oral poliovirus vaccines (OPV) administered based on the reported immunization data. Risk was calculated as the ratio between the number of VAPP cases and the number of OPV doses administered. Both the Runs test and the Poisson model were used to analyze the occurrence of VAPP. Thirty-three cases of VAPP were recorded in Japan between 1971 and 2000; approximately one case occurred per year. There were no statistical changes in temporal trends as regards the occurrence of VAPP between 1971 and 2000. The overall risk for VAPP, including both recipient and contact VAPP, was one case per 2.0 million OPV doses administered. The risk of recipient VAPP was one per 3.7 million doses, among which the first dose posed a much higher risk of one per 2.3 million than that of the subsequent dose. These data indicated that the occurrence of VAPP is rare, but the risk has remained constant for as long as OPV has been used in Japan.

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