The Trump administration has intensified its examination of the measles, mumps, and rubella (MMR) vaccine amid the most severe measles outbreak in recent memory.
On Monday, Jim O’Neill, acting director of the US Centers for Disease Control and Prevention (CDC) and deputy secretary of the Department of Health and Human Services (HHS), advocated for the development of new vaccines to replace the existing combined MMR formulation.
In a message posted on X/Twitter, O’Neill urged vaccine producers to create safe monovalent vaccines, effectively separating the MMR vaccine into three distinct injections.
He referenced a tweet from former President Donald Trump dated September 26, which discouraged the use of Tylenol alongside “mixed” vaccines and suggested postponing the hepatitis B vaccine from birth until the age of 12.
Currently, many childhood immunizations are combined to minimize the number of injections children must receive, a practice supported by decades of scientific evidence confirming their safety and effectiveness.
Jason Schwartz, an associate professor at Yale School of Public Health, described the proposal to separate these vaccines as an unnecessarily complex, costly, and time-intensive endeavor.
Increasing the number of shots would not only raise vaccination costs but also require more frequent pediatric visits. If all vaccines were administered individually, a six-month-old infant would need approximately 20 appointments to complete the full immunization schedule.
Schwartz emphasized that the added logistical burden could lead to lower completion rates of the MMR series, as parents might struggle to keep up with the increased number of visits and follow-ups.
Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia and co-developer of a rotavirus vaccine, stated that fragmenting the MMR vaccine serves no practical purpose, especially given the existing financial challenges in healthcare.
Certain vaccines, such as the diphtheria, tetanus, and pertussis (DTaP) vaccine, are only available as combination shots and cannot be separated. While monovalent vaccines for measles, mumps, and rubella were once licensed in the 1960s, the combined MMR vaccine is now the sole option in the United States.
The MMR vaccines currently distributed by Merck and GSK have been affirmed by both companies as safe and effective, with no scientific data supporting the need to separate them. They also highlight that combination vaccines simplify immunization and reduce costs.
Under the Trump administration’s new policies, introducing separate vaccines would necessitate entirely new clinical trials using saline placebos, a process described by Schwartz as “unimaginable” given the proven safety of existing vaccines.
Angela Rasmussen, a virologist at the University of Saskatchewan’s Vaccine and Infectious Disease Organization, called such trials “incredibly unethical,” as they would expose infants to potentially deadly diseases without protection.
She added that no ethical review board would approve these studies, nor would healthcare providers or families consent to participate, making such trials virtually impossible.
A scheduled meeting of the CDC’s Advisory Committee on Immunization Practices (ACIP) for October 22-23 has been postponed indefinitely.
Schwartz noted the uncertainty surrounding the committee’s future actions, pointing out that while ACIP might express interest in monovalent vaccines, none are currently approved for recommendation.
During a September meeting, ACIP members initiated discussions about delaying the hepatitis B vaccine, which is presently recommended at birth, but deferred the decision.
Since later hepatitis B doses are typically administered as part of combination vaccines, any change in this recommendation would impact those formulations.
Offit expressed skepticism about the scientific basis of the committee’s deliberations, suggesting that decisions may be influenced more by anti-vaccine sentiments than by empirical evidence.
He recalled that the question of separating the MMR vaccine was thoroughly addressed by ACIP over twenty years ago.
Offit, who served on ACIP from 1998 to 2003, referenced the now-discredited study by Andrew Wakefield, which falsely claimed a link between the combined MMR vaccine and autism.
Wakefield had filed a patent for a monovalent measles vaccine prior to publishing his study but failed to disclose this conflict of interest.
He alleged that the combined vaccine compromised the immune system, leading to autism, a claim for which no evidence was ever found, according to Offit.
Following the publication, ACIP voted against altering the MMR vaccine recommendation, supported by epidemiological data showing no association between vaccination and autism.
In a recent development, ACIP voted in September to remove the recommendation for the combined MMR and varicella (chickenpox) vaccine, a change the CDC adopted last week, causing confusion among healthcare providers and patients.
Schwartz warned that increasing complexity and uncertainty in vaccination protocols can significantly hinder immunization efforts for families and medical professionals alike.
Rasmussen added that fragmenting vaccines into monovalent forms could reduce accessibility, as vaccines sitting unused on shelves are effectively useless, a situation that anti-vaccine advocates might welcome.
