From the Guidelines
The MMR vaccine schedule changed from one dose to two doses in 1989. Prior to this change, a single dose was recommended for children, typically administered at 12-15 months of age. However, after observing measles outbreaks among previously vaccinated children and adolescents in the late 1980s, the Advisory Committee on Immunization Practices revised the recommendation to include a second dose, as stated in the 1998 report 1. The current two-dose schedule calls for the first dose at 12-15 months of age and the second dose at 4-6 years of age, before children enter school. This change was implemented because studies showed that approximately 5-10% of individuals did not develop adequate immunity after a single dose, as mentioned in the context of the 1989 recommendation change 1. Adding the second dose increases the effectiveness of the vaccine to approximately 97-99% protection against measles, mumps, and rubella. The two-dose schedule has been instrumental in dramatically reducing the incidence of these diseases in countries with high vaccination coverage and remains the standard recommendation for MMR vaccination worldwide, with the specific age for the second dose being recommended at 4-6 years by the Advisory Committee on Immunization Practices 1.
Some key points to consider include:
- The change to a two-dose schedule was recommended by both the Advisory Committee on Immunization Practices (ACIP) and the American Academy of Pediatrics (AAP) in 1989, as noted in the report 1.
- The second dose is recommended to be administered before school entry, at 4-6 years of age, as specified in the 1998 recommendations 1.
- The two-dose schedule provides a higher level of protection against measles, mumps, and rubella, with approximately 97-99% effectiveness, which is crucial for reducing the incidence of these diseases in countries with high vaccination coverage.
From the Research
MMR Vaccine Recommendation Change
The change from a one-dose to a two-dose schedule for the Measles, Mumps, and Rubella (MMR) vaccine is supported by several studies.
- The exact year of the recommendation change is not specified in the provided studies, but the studies suggest that a two-dose schedule is more effective in preventing measles, mumps, and rubella outbreaks 2, 3.
- A study published in 2002 found that a large proportion of pre-school children had measles and mumps IgG antibody below the putative level of protection after receiving a first dose of MMR vaccine, but the proportion negative to one or more antigens dropped to <4% after a second dose of MMR vaccine 2.
- Another study published in 2020 found that the effectiveness of the MMR vaccine in preventing measles was 95% after one dose and 96% after two doses, and the effectiveness in preventing mumps was 72% after one dose and 86% after two doses 3.
- The studies suggest that the two-dose schedule is recommended to ensure long-term protection against measles, mumps, and rubella, and to prevent outbreaks in highly vaccinated populations 2, 4, 3.
Key Findings
- A two-dose schedule of MMR vaccine is more effective in preventing measles, mumps, and rubella outbreaks than a one-dose schedule 2, 3.
- The effectiveness of the MMR vaccine in preventing measles and mumps increases with a second dose 2, 3.
- The two-dose schedule is recommended to ensure long-term protection against measles, mumps, and rubella, and to prevent outbreaks in highly vaccinated populations 2, 4, 3.