With measles cases hitting record highs in recent years, many are asking a critical question: Can you still get measles if you’ve had the vaccine?
The short answer is yes, but it is extremely rare. While the measles vaccine is one of the most effective tools in public health history, no vaccine is 100% effective.
Here is a skimmable breakdown of why breakthrough cases happen, how the math works, and why being vaccinated still offers a massive advantage.
1. How Effective is the Measles Vaccine?
The Measles, Mumps, and Rubella (MMR) vaccine is the gold standard for protection. According to the CDC, its effectiveness depends on the number of doses:
- One Dose: Approximately 93% effective at preventing infection.
- Two Doses: Approximately 97% effective.
For most people, these two doses provide lifelong immunity.
2. Why Breakthrough Infections Occur
If 100 people who have received two doses are exposed to the virus, about 3 of them may still get sick. These are called “breakthrough infections.” There are two main reasons for this:
- Primary Vaccine Failure: A small subset of people simply do not develop a sufficient immune response after vaccination.
- Secondary Vaccine Failure: In rare cases, a person’s immunity may wane over many years, or their immune system may be overwhelmed by intense, prolonged exposure to the virus.
3. The “Vaccinated Advantage”
Even if you are among the rare few who get a breakthrough infection, being vaccinated provides two major benefits:
- Milder Symptoms: Vaccinated patients typically experience much milder illness and are significantly less likely to suffer from severe complications like pneumonia or brain swelling.
- Less Contagious: Research suggests that vaccinated individuals who contract measles are less likely to spread the virus to others.
4. Do You Need a Booster?
Most healthy adults who received two doses as children do not need a booster. However, you should consult your healthcare provider if:
- You only received one dose.
- You were vaccinated between 1963 and 1967, when an earlier, less effective “killed” version of the vaccine was used.
- You are a healthcare worker or planning international travel to areas with active outbreaks.
Quick Fact Check
| Status | Effectiveness | Risk After Exposure |
|---|---|---|
| Unvaccinated | 0% | ~90% chance of infection |
| 1 Dose MMR | 93% | ~7% chance of infection |
| 2 Doses MMR | 97% | ~3% chance of infection |
Source: CDC Measles Clinical FAQ
Are you unsure of your vaccination status? You can often verify your immunity through a simple blood test called a titer test, or you can use the CDC’s guide on finding vaccine records.