Why the MMR vaccine is given as one shot, and what separating it into more could mean

Key Points:

• President Donald Trump signed an executive order recommending the MMR vaccine be split into three separate shots, claiming without evidence that individual immunizations are safer.
• Medical experts and public health organizations criticized the order, stating decades of research confirm the combined MMR vaccine is safe, effective, and more convenient, while splitting it would increase missed vaccinations amid a measles outbreak.
• The combined MMR vaccine, available since 1971, triggers an immune response comparable to individual vaccines and reduces the number of doctor visits required, which is crucial during the current highest measles incidence in over 30 years.
• No monovalent MMR vaccines are currently licensed or planned for use in the U.S., and developing them would be costly and time-consuming; pharmaceutical companies like Merck see no scientific benefit to splitting the vaccine.
• Claims linking vaccines to autism and overwhelming the immune system have been debunked by extensive research, with experts emphasizing that vaccines contain fewer active antigens than past vaccines and do not impair immune function.