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For children, rubella typically means a few days of fever and rash — mild and unremarkable. But when a pregnant woman in her first trimester is infected, the virus can cross the placenta and cause serious fetal harm — a condition known as congenital rubella syndrome (CRS).
"I'm a child; if I get it, it won't be serious." "There are no pregnant women around me." Neither framing addresses the real risk. With rubella, the problem does not occur in the person who is infected — it occurs in the fetus of a pregnant person that infected person may happen to encounter.
What Is Congenital Rubella Syndrome (CRS)?
When a woman is infected with rubella virus early in pregnancy — particularly before eight weeks of gestation — the virus crosses the placenta and can cause congenital abnormalities. The risk of fetal defect is 85–90% for infections occurring at one to eight weeks of gestation [1]. The classic triad of CRS is congenital heart disease, cataracts: clouding of the eye's lens causing blurred or blocked vision, requiring surgical treatment in infants, and hearing loss.
Risk decreases as pregnancy advances. By 20 weeks of gestation, fetal effects are considered negligible. But the critical window — early pregnancy — frequently includes weeks when the woman does not yet know she is pregnant, making prevention especially difficult [1,2].
Asymptomatic infection adds another layer of complexity. An estimated 20–50% of rubella infections are asymptomatic: producing no noticeable symptoms despite active infection [2]. The absence of a rash is not reassuring.
A Japan-Specific Problem: A Generation Without Vaccination
While most countries routinely vaccinate both boys and girls against rubella as part of MMR, Japan administered rubella vaccine only to middle-school girls between 1977 and 1994. Men born roughly between 1962 and 1979 were never offered rubella vaccination as part of the routine childhood schedule. This unprotected generation of men became the primary source of major rubella outbreaks in 2013–2014 and 2018–2019, during which multiple CRS cases were reported [3,4].
Japan's Fifth-Round Supplementary Immunization Program (2019–2024)
In response to the 2018–2019 outbreak, Japan's Ministry of Health, Labour and Welfare implemented a five-year program (2019–2024) offering free rubella antibody testing and vaccination specifically to men born between 1962 and 1979 — the fifth round of targeted supplementary immunization [4]. That program closed in March 2024. The fact that catch-up immunization of adult men was a major pillar of Japan's rubella response for five years is worth understanding in context.
How Children's Vaccination Supports the Whole Community
The MR vaccine (measles-rubella combination) is part of the routine Japanese immunization schedule: two doses, the first at one year of age (first series) and the second the year before primary school entry (second series). Two-dose coverage with the rubella component achieves 97–99% or greater protection [2].
Completing a child's MR vaccination is not only a personal health measure. It contributes to the community-level immunity that prevents rubella from reaching pregnant women. The answer to "why does my child need the MR vaccine?" includes the social purpose of CRS prevention.
What Parents Can Do
- Confirm that both MR doses (first and second series) are recorded in the boshi techo (Maternal and Child Health Handbook).
- If you are planning a pregnancy, consider having a rubella antibody titer: blood test measuring the level of protective antibodies to determine whether immunity to rubella is adequate test beforehand and, if immunity is insufficient, receiving a vaccine dose (vaccination during pregnancy is contraindicated, so it must be completed before conception).
- If a pregnant person lives in your household, thorough handwashing and respiratory hygiene reduce transmission of rubella along with other respiratory infections generally.
Summary
The goal of rubella prevention is not about how sick you personally would get — it is about whether the herd immunity in your community is strong enough to protect pregnant women and the fetuses they are carrying. Completing a child's two-dose MR vaccination is both a personal safeguard and a contribution to that collective protection. Keeping that vaccination record — and being able to check it — is where that contribution begins.
References
- Bouthry E, Picone O, Hamdi G, Grangeot-Keros L, Ayoubi JM, Vauloup-Fellous C. Rubella and pregnancy: diagnosis, management and outcomes. Prenat Diagn. 2014;34(13):1246–1253. doi:10.1002/pd.4467. PMID: 25056283.
- Reef SE, Plotkin S, Cordero JF, et al. Preparing for elimination of congenital rubella syndrome (CRS): summary of a workshop on CRS elimination in the United States. Clin Infect Dis. 2000;31(1):85–95. doi:10.1086/313928. PMID: 10913400.
- Yoshida N, Uchida K, Kase T. Rubella vaccines in Japan: time to act now. Lancet Infect Dis. 2015;15(8):880–881. doi:10.1016/S1473-3099(15)00085-0. PMID: 26194031.
- Ministry of Health, Labour and Welfare (Japan). Special rubella prevention policy (fifth round). 2018.
- National Institute of Infectious Diseases (Japan). Rubella and congenital rubella syndrome surveillance. IASR. 2024.
- Kakoulidou M, Forsgren M, Lewensohn-Fuchs I, Johansen K. Seropositivity for rubella in Swedish women after change of vaccination strategy. Vaccine. 2010;28(3):774–778. doi:10.1016/j.vaccine.2009.10.091. PMID: 19878751.