Splitting MMR Would Repeat Japan's Vaccine Mistakes
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- Maurice Hilleman developed the mumps vaccine in 1967 from his daughter Jeryl Lynn's virus and combined it into the MMR vaccine, licensed in 1971 and still manufactured by Merck.
- Trump's executive order calls for splitting MMR into separate shots, a move the article says would mean more missed vaccine doses and more sick children.
- Japan pulled its MMR vaccine in 1993 after the 1989 version (a different mumps strain) was linked to meningitis; mumps remains endemic with 300+ hearing-loss cases in 2015-16, and a 2001 measles outbreak affected an estimated 265,000 children.
- A Stanford modeling study estimates a 10% decrease in MMR vaccination would produce 11 million measles cases over 25 years.
- No single-dose measles, mumps, or rubella vaccines are currently marketed in the U.S., leaving open how separate shots would become available.
- Numerous studies have shown MMR does not increase autism risk, and Japan's MMR withdrawal had no effect on autism rates.
- Before vaccines, measles caused 48,000 hospitalizations and about 500 deaths annually in the U.S., and the 1964-65 rubella epidemic caused 20,000 infants to be born with congenital rubella syndrome.
Why it matters: Japan is the warning: after pulling MMR in 1993, mumps never went away and a 2001 measles outbreak hit 265,000 children. Stanford modeling says a 10% U.S. MMR drop would generate 11 million measles cases over 25 years — and no single-dose alternatives are even on the U.S. market.
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