Can you get measles if you've been vaccinated?

The short answer is yes, but it is extremely rare.

According to the Oklahoma State Department of Health, the measles, mumps, and rubella (MMR) vaccine is highly effective in preventing measles, but no vaccine offers 100% protection. However, the chances of contracting measles after being vaccinated are very low.

Effectiveness of the MMR Vaccine

The MMR vaccine is about 93% effective at preventing measles after one dose and 97% effective after two doses. For most people who receive the recommended doses, the vaccine provides long-term protection.

However, breakthrough cases—instances where vaccinated individuals contract the disease—can occur, especially in specific circumstances:

1. Incomplete Vaccination
2. If an individual did not receive both recommended doses of the MMR vaccine, their protection against measles may not be as strong, increasing the risk of infection.
3. Weakened Immune System
4. Individuals with weakened immune systems (due to conditions such as HIV/AIDS or certain medications) may have a reduced response to the vaccine, making them more susceptible to contracting measles despite being vaccinated.
5. Outbreaks in High-Risk Areas
6. Measles is highly contagious, and outbreaks in areas with low vaccination rates can lead to higher chances of exposure. For example, the Oklahoma State Department of Health recently reported two measles cases linked to an outbreak originating in Texas and New Mexico. While the individuals who contracted the virus had been vaccinated, they were exposed to a large outbreak. Health officials stress that the MMR vaccine is still effective, and in the event of exposure, those who are not immune through vaccination or prior infection should follow precautions, including self-isolation for 21 days.
7. Vaccine-Related Factors
8. Like all vaccines, the MMR vaccine is not perfect. Some individuals may not respond as effectively to the vaccine, even if they receive both doses. However, these cases are rare and often occur in populations where the overall vaccine response is lower.

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