Vaccine skeptics are one step closer to their long-term goal of having separate vaccines for measles, mumps, and rubella, with support from the Trump administration, even as they face pushback from the pharmaceutical industry and medical establishment.

President Donald Trump and Deputy Health Secretary Jim O’Neill shocked the medical community earlier this month by calling for vaccine makers to produce three new separate vaccines instead of the currently approved MMR shot that combines all three.

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Public health experts criticizing O’Neill and Trump’s comments have highlighted that no single-virus, or monovalent, vaccines for measles, mumps, and rubella are on the market in the United States.

That is only a comparatively recent development, though. Monovalent vaccines for the three infectious diseases were on the market in the United States from their development in the 1960s until Merck discontinued them in 2009. The combined MMR vaccine was launched by Merck in 1971 and was the strong preference of the medical community until it eventually became the only option for patients. 

But vaccine-skeptical parents began to develop a preference for the monovalent vaccines following the publication of a paper, now regarded as fraudulent, linking the MMR vaccine to autism, published by the journal The Lancet and written by British physician Andrew Wakefield in 1998. 

O’Neill’s endorsement of separating the MMR immunizations has additional weight with his role in authorizing new vaccines as the acting director of the Centers for Disease Control and Prevention. 

HHS spokesperson Andrew Nixon told the Washington Examiner that O’Neill “agrees with President Trump” that the immunizations “would be best administered as three separate vaccines,” but he did not answer whether the administration is in discussions with pharmaceutical companies about producing single-virus vaccines. 

“Standalone vaccinations can potentially reduce the risk of side effects and can maximize parental choice in childhood immunizations,” said Nixon.

Resurgence of the single-virus vaccine narrative

Trump initially endorsed the monovalent vaccines for measles, mumps, and rubella while praising the CDC’s Advisory Committee on Immunization Practices new guidance that no longer recommends the combination vaccine that includes varicella, or chickenpox. Instead, it favors two shots: a monovalent chickenpox vaccine and the standard MMR. 

Scientists presenting at the two-day ACIP meeting last month highlighted evidence that the MMRV four-virus vaccine, referred to as MMR+V, was associated with slightly higher rates of fever-induced seizures in infants compared to the single varicella vaccine and the standard MMR. 

But the further step of recommending separate measles, mumps, and rubella vaccines has been a focal point for vaccine skeptics since the late 1990s and early 2000s. 

Dr. Jake Scott, professor of infectious disease medicine at Stanford University, told the Washington Examiner that Wakefield’s advocacy was the beginning of advocacy for so-called “single jabs,” or the monovalent measles, mumps, and rubella vaccines. 

“The separation idea appeared first at Wakefield’s 1998 media campaign around his now retracted paper that really did promote single jabs, as he called it, and to space them out over time,” Scott said.

British parents took Wakefield’s warning seriously, and demand for single-virus vaccines in the United Kingdom soared following his press conference after the initial publication of his paper in February 1998. The British National Health Service pulled the monovalent vaccines from the market by August, six months later.

Wakefield had his British medical license revoked, but has subsequently started a film production company in the U.S., making documentaries about the harms of vaccines. 

Merck decides to no longer produce single-virus MMR

It’s not clear from public records why Merck decided to pull the monovalent vaccines from the market. 

ACIP meeting minutes from October 2009 indicate that committee member Dr. Cody Meissner inquired during the meeting about the conflicting messaging between the CDC’s website, which was highly supportive of the MMR combo vaccine, and the written guidance, which was less affirmative. 

The CDC cited at the time that “separating the doses puts children and pregnant women who may be exposed to them at increased risk for these decisions by extending the time children remain unvaccinated.”

The agency also cited evidence that multiple vaccines present “an increased risk that their children may not receive all the vaccines they need” because they had to schedule more doctors’ appointments. 

Dr. Mark Feinberg, representing Merck at the time, responded to Meissner’s concerns by saying that the meeting and consultation with ACIP members during the prior meeting, as well as discussions with the scientific community, led Merck to decide not to resume production of monovalent measles, mumps, and rubella vaccines. 

When asked this month by the Washington Examiner for more context on the company’s decision, a Merck spokesperson said that the company chose to prioritize the MMR multivalent vaccine in 2009 “based on input from the Advisory Committee on Immunization Practices, professional societies, scientific leaders, and customers.”

Meissner, appointed by HHS Secretary Robert F. Kennedy Jr. this summer to serve again on ACIP, did not respond to the Washington Examiner’s request for comment. 

Industry reticent to make new single-virus vaccines

Scott told the Washington Examiner that, even if there were demand for monovalent measles, mumps, and rubella immunizations, vaccine manufacturers would face significant hurdles to bring them to market. 

Although single-virus vaccines were a feature of the not-too-distant past, Scott said companies would need to navigate the complex production of vaccines, from clinical trials to manufacturing facilities, and the FDA regulatory process to bring three new vaccines to market instead of one. 

“It’s not like a label tweak; it’s a whole program. It’s not just a flip of a switch,” said Scott. “It’s years of work and a step away from the simpler schedule that helps kids clearly finish their vaccine schedule.”

The Merck spokesperson did not respond to questions regarding whether Merck would consider relaunching its monovalent vaccines, but said that there is “no published scientific evidence that shows any benefit in separating the combination MMR vaccine into three individual shots.”

“Use of the individual components of combination vaccines increases the number of injections for the individual and may result in delayed or missed immunizations,” the Merck spokesperson said.

A spokesperson from GlaxoSmithKline, which received approval from the Food and Drug Administration for its MMR vaccine in 2022, told the Washington Examiner that “combination vaccines play a crucial role in improving vaccination coverage rates.” 

“Their safety and efficacy have been demonstrated by decades of research. By reducing the number of separate injections required, combination vaccines allow for a simpler and more efficient immunization process, which is essential for timely protection against disease,” said the GSK spokesperson.

Neither GSK nor Merck answered questions from the Washington Examiner gauging their interest in investing in the production of new monovalent vaccines. 

Japanese pharmaceutical company Daiichi Sankyo produces a monovalent mumps vaccine that is voluntary in Japan, and Russian company Microgen makes a monovalent rubella vaccine. Neither company responded to the Washington Examiner’s request for comment. 

HHS did not comment on industry concerns about producing monovalent vaccines or the timeline for producing vaccine alternatives to the two currently approved MMR shots.