From the Guidelines
Despite receiving three doses of the measles vaccine with a booster six months ago, you may still not be immune to measles due to primary vaccine failure or other factors that interfere with immune response. The most common explanation is primary vaccine failure, where your body simply didn't produce enough protective antibodies in response to the vaccine, occurring in about 2-5% of people who receive the recommended doses 1. Other factors that might interfere with developing immunity include:
- Immune system disorders
- Certain medications that suppress immune function
- Improper vaccine storage or administration
- Rarely, genetic factors that affect how your body responds to vaccines To determine why you specifically didn't develop immunity, blood testing to measure your antibody levels would be helpful, as recommended by the advisory committee on immunization practices 1. You should consult with your healthcare provider, who might recommend an additional booster dose or protective measures during measles outbreaks, such as a third dose of MMR for persons identified by public health authorities as being part of a group or population at increased risk for acquiring mumps because of an outbreak 1. While this situation is uncommon, it highlights why high vaccination rates in communities are important to protect those who cannot develop immunity despite proper vaccination, and the importance of following the recommended vaccination schedule, including a second dose of MMR separated by ≥28 days for travelers aged ≥12 months who have not received 2 doses of MMR 1.
From the FDA Drug Label
The FDA drug label does not answer the question.
From the Research
Measles Immunity After Vaccination
- The measles vaccine is highly effective, but immunity can wane over time 2, 3, 4.
- Studies have shown that two doses of the measles, mumps, and rubella (MMR) vaccine are 97% effective against measles, but some individuals may still be susceptible to infection 2.
- A third dose of the MMR vaccine may not provide significant additional protection against measles, as most individuals are already seropositive after two doses 2.
Factors Affecting Measles Immunity
- The age at which the first MMR vaccine is administered can affect the level and duration of immunity, with earlier vaccination potentially leading to faster antibody decay 3.
- The presence of neutralizing antibodies is an important factor in determining immunity to measles, but other factors such as cell-mediated immunity and antibody avidity may also play a role 2, 5.
- Naturally acquired immunity to measles, resulting from infection rather than vaccination, may provide longer-lasting protection than vaccine-induced immunity 4.
Booster Vaccination and Measles Immunity
- Booster vaccination can provide a significant increase in measles antibody titers, but the effect may be limited in individuals with pre-existing immunity 4.
- The need for booster vaccination may depend on various factors, including the individual's vaccination history, age, and risk of exposure to measles 6, 4.
- More research is needed to determine the optimal vaccination schedule and booster strategy for maintaining measles immunity in different populations 2, 3, 4.