The measles outbreak that started in Texas in late January continues to grow. As of March 27, 2025, confirmed cases across the United States reached 483, surpassing the total number of confirmed cases recorded in 2024. About 93 percent of the cases are associated with the outbreak, which now spans Texas, New Mexico and Oklahoma.
Most people who have received the live measles vaccine won’t need an additional shot now, but certain groups may benefit from a second dose. People born before 1957 are presumed to have lifelong immunity due to widespread measles infections before age 15. Those born after 1957 should be set for life unless they fall into high-risk categories.
Exceptions include individuals vaccinated between 1963 and 1967 with an inactivated vaccine, which may require a live dose, or those in high-risk groups like healthcare providers, international travelers, or college students who haven’t had one dose yet. There is no recommendation for a third dose of the measles vaccine.
The vast majority of cases are in people not vaccinated. The lack of clarity from health authorities leaves many with questions about revaccination. To determine immunity status, antibody levels can be checked, but this test may not accurately reflect immunity and should only be done in specific cases with consultation from a doctor.
Natural immunity is effective but comes with risks like hospitalizations and severe brain inflammation. Vaccines create immunity without these risks. The current vaccine strain is 97 percent effective, and breakthrough cases are likely to be milder than a full-blown case of measles.
The vaccine cannot cause measles due to its weakened strain, and the recent outbreak was caused by a wild virus, not the vaccine itself. While the vaccine has worked well, it’s essential to weigh its risks against potential benefits.
Source: https://www.pbs.org/newshour/health/do-adults-need-a-measles-booster-an-epidemiologist-explains-who-is-immune