The MMR vaccine-induced suffering refers to severe adverse reactions—such as acute encephalitis and aseptic meningitis—among infants and young children who received the combined live-attenuated measles (M), mumps (M), and rubella (R) vaccine. Although incorporated into Japan’s routine immunization program in April 1989, the Maebashi Medical Association soon reported a high incidence of aseptic meningitis among recipients. Government inaction allowed the suffering to spread until inoculation was suspended in 1993, by which time approximately 1,800 children had been affected. It was later revealed that a pharmaceutical company had altered the mumps vaccine culture method without notifying the authorities.
| 1989 | Health damage occurs [April 1989 (start of routine vaccination) – April 1993] Report by the Maebashi City Medical Association |
| 1993 | Three families file lawsuits against the government and pharmaceutical company Government suspends vaccinations for the time being |
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1. The mumps vaccine and the emergence of harm
The MMR vaccine combined immunizations for measles (M), mumps (M), and rubella (R). Initially, original-strain vaccines produced by separate companies were mixed and approved individually. To implement nationwide routine vaccination, however, the former Ministry of Health and Welfare (MHW) directed that a “standardized-strain vaccine” be manufactured by combining strains deemed effective from several companies. Among these, the mumps vaccine produced by the Research Foundation for Microbial Diseases of Osaka University was later found responsible for causing aseptic meningitis. The standardized MMR vaccine was intended to replace earlier in-house strains that had already been discontinued. Nevertheless, expired stocks were used, and the pharmaceutical company unilaterally changed the viral culture method—without authorization—to increase vaccine potency. Despite existing reports from Canada and within Japan on adverse effects of MMR vaccines, the Japanese government proceeded to legalize routine immunization in 1989. At that time, questions had already been raised in the MHW’s own Vaccine Advisory Committee regarding the manufacturing process, but production continued without stricter controls. Immediately after the program’s introduction, many infants developed aseptic meningitis accompanied by fever, vomiting, and convulsions. In June 1989, just two months after routine inoculation began, the Maebashi Medical Association started collecting data on side effects, reporting meningitis in approximately 1 in every 217 children. The MHW neither responded nor disclosed the data. A notice urging “cautious administration” was issued in October 1989, yet vaccinations continued until 1993. It is now known that an informal advisory committee within the Ministry debated suspending the program but failed to act, concealing data on adverse reactions and delaying a decision to halt inoculation. Between 1989 and 1993, approximately 1.83 million infants received the MMR vaccine, and 1,754 cases of aseptic meningitis were officially reported.
2. Lawsuits by affected families
In 1993, three families whose children had developed aseptic meningitis after receiving the MMR vaccination filed suit against the state and the pharmaceutical company. Of the three children evaluated, causality was recognized for two, while the claim of the third was dismissed. The company did not appeal; instead, it issued a formal apology and reached an out-of-court settlement—effectively acknowledging responsibility. Both the parents and the government appealed the partial ruling, and the remaining family filed a cross-appeal. After 13 years of litigation, the Supreme Court dismissed the parents’ final appeal in 2006, bringing the long battle to an end. The court held that the pharmaceutical company’s unauthorized change in the mumps vaccine production method had caused the surge in harm and that the government bore responsibility for inadequate supervision. Both were ordered to compensate the victims. However, the state’s failure to suspend the program promptly was not deemed a legal violation. While plaintiffs demanded a formal apology, the government rejected the request, stating that the judgment was “unacceptable.”
3. Aftermath and continuing challenges
The large-scale outbreak of aseptic meningitis and the subsequent suspension of the MMR program seriously eroded public trust in vaccination. Consequently, Japan’s measles immunization rate fell dramatically, leaving it one of the few developed countries still reporting frequent measles cases. Despite court rulings, the government has yet to issue a formal apology or to clarify the full causes of the MMR vaccine adverse events, nor has it implemented comprehensive prevention measures. Misconceptions about the incident persist even within pharmaceutical regulation, reflecting broader problems in Japan’s risk communication and vaccine governance. In recent years, new vaccines—including HPV and COVID-19 vaccines—have been introduced. The lessons of the MMR tragedy underscore the importance of transparency, prompt action, and independent safety oversight to prevent further erosion of public confidence.
References
- The Pharmaceutical and Medical Device Regulatory Science Society of Japan (2012), 『知っておきたい薬害の教訓――再発防止を願う被害者からの声』YAKUJI NIPPO, (ISBN 4840812136).
- The Pharmaceutical and Medical Device Regulatory Science Society of Japan Pharmacopoeia Association (2011), 『知っておきたい薬害の知識』Jiho, (ISBN 4840741743).