Medical experts are advising certain groups of adults to review their immunization records as measles cases in the United States reach a 30-year high. While the infection was considered eliminated from the U.S. in 2000, clinicians report that outbreaks are now occurring domestically rather than being limited to cases imported from overseas. According to Dr. Gavin Harris of Emory Healthcare, between 38% and 40% of measles cases this year have occurred in adults, a group that accounted for more than half of measles hospitalizations in 2025.
Health officials state that the two-dose measles, mumps, and rubella (MMR) vaccine is the primary method of prevention, offering approximately 97% effectiveness. Those who received two doses after their first birthday are generally considered to have lifelong protection and do not require a booster. However, physicians are highlighting specific groups who may lack sufficient immunity, including those who cannot locate their vaccination records and individuals who received a version of the vaccine distributed between 1963 and 1967.
Dr. Geeta Sood of Johns Hopkins Medicine noted that while most people who attended public schools were likely vaccinated, those without records should consult state immunization registries or their healthcare providers. For those who remain unvaccinated, clinicians noted that receiving the vaccine within three days of exposure, or receiving intravenous immunoglobulin (IVIG) within six days, can provide protection against the illness. Measles can result in severe complications, including pneumonia, brain swelling, and death.
The impact on individuals involves potential out-of-pocket costs and time. While a titer test—a blood test that checks for existing antibodies—is an option, medical experts suggest that getting an additional vaccine dose is often more practical. A titer test can involve laboratory fees, insurance copays, and multiple trips to a clinic, whereas a booster dose is described by pharmacists as a safe alternative if records are missing. Those born before 1957 are generally considered naturally immune due to the high prevalence of the virus before the vaccine was introduced.
The domestic resurgence of the virus puts pressure on state health registries and local pharmacies as adults seek to verify their status. If an individual is exposed while unvaccinated, they must seek medical intervention within a window of 72 hours for the vaccine or six days for immunoglobulin to remain protected. Because the virus is highly contagious, health officials indicate that even a small amount of exposure can lead to infection in those without immunity. No specific legislative deadlines or court dates were reported, but health providers are urging adults to check registries or contact their doctors if their vaccination history is unclear.