Anything significant in MMR at 12mos vs. 15mos?
No. There is no correlation to disease and vaccination at 12 months of age. Infants used to be routinely vaccinated at 15 months of age. During the 1989-1991 measles resurgence, incidence rates of measles were more than twice as high as those in other age groups. The mothers of many young infants who developed measles were young, and their measles immunity was most often due to vaccination rather than infection with wild virus. As a result, a smaller amount of antibody was transferred across the placenta to the fetus, compared with antibody transfer from mothers who had higher antibody titers resulting from wild infection. The lower quantity of antibody resulted in immunity that waned more rapidly, making infants susceptible at a younger age than in the past. At this time the routine MMR vaccination age was lowered to 12 months of age. Passive immunization, maternal antibody is transferred across the placenta and appears to protect infants from developing mumps during the first year of
