From the Guidelines
The first dose of the measles vaccine is highly effective, providing approximately 93% protection against measles infection. This initial dose, typically administered as part of the MMR (measles, mumps, rubella) vaccine, is usually given to children at 12-15 months of age. While the first dose offers substantial protection, a second dose is recommended to reach optimal immunity levels of about 97% 1. The vaccine works by introducing a weakened form of the measles virus that cannot cause disease but stimulates the immune system to produce antibodies against the virus. These antibodies remain in the body and provide long-term protection against future measles infections. Some key points to consider when administering the measles vaccine include:
- The first dose is usually given at 12-15 months of age, with a second dose recommended at 4-6 years of age 1.
- For children aged 12-47 months, either MMR vaccine and varicella vaccine or MMRV vaccine may be used for the first dose, but providers should discuss the benefits and risks of both options with parents or caregivers 1.
- A personal or family history of seizures is a precaution for MMRV vaccine use, and children with such a history should generally be vaccinated with MMR vaccine and varicella vaccine instead 1. The high effectiveness of even a single dose has been instrumental in reducing measles cases worldwide, though two doses are standard in most vaccination schedules to ensure maximum protection and account for the small percentage of individuals who don't develop immunity after the first dose. For those who missed childhood vaccination, a single dose still provides significant protection if received as an adult.
From the Research
Effectiveness of the First Dose of the Measles Vaccine
- The effectiveness of the first dose of the measles vaccine in preventing measles is 95% [ 2 ].
- The vaccine effectiveness in preventing cases among household contacts or preventing transmission to others after one dose is 81% [ 2 ].
- The effectiveness of the first dose in preventing measles after exposure (post-exposure prophylaxis) is 74% [ 2 ].
Comparison with Multiple Doses
- The effectiveness of two doses of the measles vaccine is 96% [ 2 ].
- The effectiveness of two doses in preventing cases among household contacts or preventing transmission to others is 85% [ 2 ].
- A third dose of the vaccine can provide additional protection, with 96% effectiveness in preventing measles [ 3 ].
Long-term Protection
- Measles antibodies can decline over time, but protection against disease is largely retained [ 3 ].
- A study found that 93.7% of participants had protective nAb levels against measles at the 10-year visit after receiving two doses of the vaccine [ 3 ].
- Another study found that vaccine-induced measles antibodies decline with time and may fall under the protective level [ 4 ].
Safety and Efficacy
- The measles vaccine is safe and effective, with no link between the vaccine and autism [ 2, 5 ].
- The vaccine can cause side effects such as febrile seizures, but the risk is small [ 2 ].
- The vaccine is cost-effective and can help eliminate measles from a population if coverage rates are high enough [ 5 ].