VACCINESWhy the CDC Director Is Wrong About the MMR Vaccine
Jim O’Neill, acting director of the CDC – and thus the head of the agency responsible for disease control — is advocating for dismantling a vaccination program his own agency credits with eliminating rubella and reducing mumps incidence by 99%. O’Neill’s call is linked to President Trump’s similar message. There is no scientific rationale for the proposed change, and the change will pose an immediate risk without any benefit.
This week Jim O’Neill, acting director of the Centers for Disease Control and Prevention (CDC), posted on X calling for vaccine manufacturers to develop separate measles, mumps, and rubella vaccines to replace the combined MMR shot. His statement linked to President Trump’s similar message but provided no scientific rationale for the proposed change, as Reuters reported. No monovalent (single-strain) vaccines for measles, mumps, or rubella are currently licensed in the United States.
This presents an unusual situation. The head of the federal agency responsible for disease control is advocating for dismantling a vaccination program his own agency credits with eliminating rubella and reducing mumps incidence by 99%. Just this January, the CDC’s website celebrated the 20th anniversary of rubella elimination as “one of our greatest public health success stories.”
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“The head of the federal agency responsible for disease control is advocating for dismantling a vaccination program his own agency credits with eliminating rubella and reducing mumps incidence by 99%.”
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The timing matters. As of September 30, the United States has recorded 1,544 confirmed measles cases this year, with 191 hospitalizations and 3 deaths. The vast majority occurred in unvaccinated individuals. Those who were vaccinated predominantly had incomplete vaccination series, having received one dose instead of the recommended two. The problem isn’t the formulation. It’s missed doses.
O’Neill’s proposal faces immediate practical obstacles. Merck discontinued its monovalent vaccines in 2009. Creating them would require pharmaceutical companies to conduct new clinical trials, reconfigure production facilities, and secure FDA approval for three separate products. This process would take years, not months.
Data Strongly Favor Combination Vaccines
Beyond logistics, the medical evidence strongly favors combination vaccines. A 2017 study found that 69% of children who received combination vaccines completed their full vaccination series, compared to 50% of those whose parents chose single vaccines. This completion gap translates directly to disease vulnerability. Separating vaccines would triple the number of medical visits required for full protection, creating barriers particularly for families with limited resources who struggle with transportation, work absence, and healthcare access.
