Measles infections in the United States have reached a 30-year high, with thousands of cases reported nationwide and several measles-related deaths this year. By comparison, only 85 cases were recorded in 2000. The disease, which was considered eliminated in the U.S. in the 2000s, is now experiencing domestic outbreaks.
"It's incredibly contagious. It's one of the most contagious illnesses known to mankind, and it can have some really drastic complications, especially for those who are unvaccinated," said Dr. Gavin Harris, an infectious diseases physician with Emory Healthcare. Measles can lead to serious complications, including pneumonia and encephalitis (brain swelling).
While often associated with children, measles is increasingly affecting adults. "We often forget about adults getting measles ... 38% to 40% of cases this year of measles have been in adults," Harris noted. "Adults become infected at the same, if not higher, rates than children themselves."
Understanding Measles Vaccination
The measles, mumps, and rubella (MMR) vaccine, a two-dose shot, is highly effective at preventing the illness. The first dose is typically given to babies between 12 and 15 months old, with the second dose administered between 4 and 6 years old. "We do know from the almost 50 years of data that two doses are about 97% effective, and one dose is about 93% effective for reducing infection," Harris said.
Experts emphasize that measles largely infects unvaccinated individuals. "If somebody has had vaccination at all in their lives, they are very, very likely to be protected," stated Dr. Geeta Sood, an infectious diseases physician at Johns Hopkins Medicine.
Determining the Need for a Booster
For adults unsure of their vaccination status, the MMR vaccine provides lifelong protection after two doses. "In reality, if you got both doses of this vaccine, you should not need a booster dose," said Samantha Picking, senior director of immunizations at Walgreens. Many individuals who attended public schools in the U.S. are likely to have been vaccinated.
If vaccination records are unavailable, checking state immunization registries or contacting healthcare providers and pharmacists are recommended steps. Parents or childhood doctors' offices may also have historical records.
If no records can be found, or if an individual received a measles vaccine between 1963 and 1967, receiving an additional MMR dose is advised. The vaccine formulation used during those years was not considered fully effective, potentially leaving some individuals unprotected. "You can get a booster. It's absolutely safe to do so," Picking affirmed, even if one had previously received the full vaccination series.
While a blood test (titer test) can check for measles antibodies, experts suggest that for most adults, obtaining an extra dose is a more straightforward and practical approach, avoiding potential additional costs and time associated with laboratory testing.
Adults born before 1957 are generally considered to have natural immunity from measles, as the disease was nearly universal before widespread vaccination.
Post-Exposure Precautions
For unvaccinated individuals exposed to measles, prompt medical attention is crucial. The measles vaccine administered within three days of exposure can provide protection, as can IVIG immunoglobulin within six days. "If you are in the category where you don’t know if you’ve had your vaccination, because we are seeing so much of [measles] around, it would be really helpful to either get those records or to talk to your doctor," Sood advised. "In the setting where you might be exposed, just thinking that you’re vaccinated is not going to be enough."