Is it recommended to administer the second dose of the Measles, Mumps, and Rubella (MMR) vaccine earlier than usual due to recent outbreaks?

From the Guidelines

Yes, it is recommended to consider administering the second dose of the MMR vaccine earlier than the routine schedule during measles outbreaks. Typically, children receive their first MMR dose at 12-15 months and the second dose at 4-6 years of age. However, during outbreaks, the second dose can be administered as soon as 28 days after the first dose for children aged 1-4 years who have already received their first dose, as indicated by the principles outlined in 1. This accelerated schedule provides faster protection for children in high-risk areas without compromising the effectiveness of the vaccine. The MMR vaccine contains live attenuated viruses that stimulate the immune system to develop protection against measles, mumps, and rubella. The first dose typically provides about 93% protection against measles, while the second dose brings this up to approximately 97%, highlighting the importance of the second dose in achieving adequate population immunity to prevent measles outbreaks, as discussed in 2. Early administration of the second dose during outbreaks helps to close immunity gaps in the community more quickly, which is crucial for controlling the spread of these highly contagious diseases, particularly measles which can spread rapidly in unvaccinated populations. Some key points to consider include:

• The recommended timing for the second dose of MMR vaccine is typically when children are aged 4-6 years, as jointly adopted by ACIP, the American Academy of Pediatrics (AAP), and the American Academy of Family Physicians (AAFP) 3.
• The use of combination measles, mumps, rubella, and varicella vaccine is recommended, with specific guidelines for its use in different age groups and scenarios, as outlined in 4.
• The purpose of the two-dose vaccination schedule is to produce immunity in the small proportion of persons who fail to respond immunologically to one or more of the components of the first dose, emphasizing the role of the second dose in ensuring comprehensive protection 2.

From the Research

Administering the Second Dose of MMR Vaccine Earlier

• The current recommendation for the MMR vaccine is two doses, with the first dose administered at age 12 through 15 months and the second dose at age 4 through 6 years before school entry 5.
• However, there have been recent outbreaks of measles, particularly affecting children between the ages of 1 and 5 years, which may raise questions about the timing of the second dose 6.
• Some studies suggest that administering the second dose of MMR vaccine earlier than recommended may be justified under special circumstances, such as traveling abroad or poor response to the first dose as evidenced by titer levels 6.
• The effectiveness of the MMR vaccine in preventing measles is 95% after one dose and 96% after two doses, and the vaccine has been shown to be safe and effective in preventing cases of measles, mumps, and rubella 7.
• The Advisory Committee on Immunization Practices (ACIP) has not revised its recommendation for the timing of the second dose of MMR vaccine in response to recent outbreaks, but the committee does recommend that individuals at high risk for exposure and transmission, such as healthcare personnel and international travelers, receive two doses of the vaccine 5.
• The challenges to implementing an earlier second dose of MMR vaccine include the need for additional resources and infrastructure to support the administration of the vaccine, as well as the potential for waning immunity over time 8, 9.

Special Considerations

• Individuals with human immunodeficiency virus (HIV) infection may require a different vaccination schedule, with the second dose of MMR vaccine recommended at age 4 through 6 years 5.
• The MMR vaccine has been shown to be safe and effective in preventing cases of measles, mumps, and rubella, even in individuals with compromised immune systems 7.
• However, the vaccine may not provide adequate protection against mumps in certain populations, such as close contact, high-density settings, and individuals who have received a second dose 10 or more years previously 8.