Quick Read
- Breakthrough measles infections are rare but possible in fully vaccinated individuals.
- Two doses of the MMR vaccine provide 97% protection against measles.
- Breakthrough cases are generally milder and less contagious.
- Causes include vaccine handling issues, immune response failure, or waning immunity.
- Experts emphasize the importance of vaccination to prevent outbreaks.
What Are Breakthrough Measles Infections?
Breakthrough measles infections refer to cases where individuals contract measles despite being fully vaccinated with the measles, mumps, and rubella (MMR) vaccine. While the MMR vaccine is highly effective, with a 97% efficacy rate after two doses, no vaccine offers absolute immunity. According to the Centers for Disease Control and Prevention (CDC), approximately three out of every 100 fully vaccinated individuals may still contract measles if exposed to the virus. These cases, however, are rare and typically milder compared to infections in unvaccinated individuals.
How Effective Is the MMR Vaccine?
The CDC recommends two doses of the MMR vaccine, with the first dose administered between 12 and 15 months of age and the second between 4 and 6 years old. The first dose provides 93% protection, while the second dose increases this to 97%. Most individuals who receive both doses develop lifelong immunity. However, a small percentage may still experience breakthrough infections due to various factors, including immune response failure or improper vaccine storage.
Causes of Breakthrough Infections
Experts identify two primary reasons for breakthrough measles infections: primary vaccine failure and secondary vaccine failure. Primary vaccine failure occurs when an individual’s immune system does not respond adequately to the vaccine. This affects about 7% of people after the first dose, but the second dose typically resolves this issue. Secondary vaccine failure, on the other hand, involves a waning immune response over time, which may occur in older adults or immunocompromised individuals.
Other factors contributing to breakthrough cases include improper handling or storage of the vaccine, which can render it less effective. Maintaining a proper cold chain during vaccine storage is crucial to preserving its efficacy. Additionally, genetic predisposition or prolonged exposure to an infected individual may increase the likelihood of a breakthrough infection.
Severity and Contagiousness of Breakthrough Cases
Breakthrough infections are generally less severe than cases in unvaccinated individuals. Symptoms such as fever, rash, and respiratory issues tend to be milder, and complications are significantly reduced. For instance, a 2020 study on a measles outbreak in the Netherlands found that vaccinated individuals who contracted measles experienced no complications or hospitalizations, whereas 14.5% of unvaccinated cases required hospitalization.
Moreover, vaccinated individuals with breakthrough infections are less likely to transmit the virus to others. This is because their viral load is typically lower, and the duration of contagiousness is shorter. Nonetheless, they can still pose a transmission risk, particularly in communities with low vaccination rates.
Importance of Vaccination
Despite the possibility of breakthrough infections, experts emphasize the critical role of vaccination in controlling measles outbreaks. Measles is one of the most contagious viruses, capable of infecting up to 90% of unvaccinated individuals exposed to it. The virus can linger in the air and on surfaces for up to two hours, making it highly transmissible.
Achieving herd immunity, which requires at least 95% of the population to be vaccinated, is essential to preventing widespread outbreaks. Vaccination not only protects individuals but also limits the virus’s ability to spread within communities.
As measles cases continue to rise in certain regions, experts anticipate an increase in breakthrough infections simply due to higher exposure rates. However, they stress that these cases are not a cause for alarm. The MMR vaccine remains one of the most effective tools in preventing severe illness and complications associated with measles. Dr. Amy Arrington of Baylor College of Medicine notes that while no vaccine is perfect, the benefits of vaccination far outweigh the risks. “Whenever population immunity is less than 95%, we see outbreaks,” she explains. “The outbreak will continue to spread as long as a fraction of the population is unvaccinated.” Ultimately, maintaining high vaccination rates is crucial to safeguarding public health and minimizing the impact of measles outbreaks.
Source: CDC, ABC News, The Dallas Morning News