The reason officially given for the second measles vaccine dose
Age for Routine Administration of the Second Dose of Measles-Mumps-Rubella Vaccine - AAP
Because most measles vaccine failures are attributable to failure to respond to the first dose, that all children receive two doses of measles-containing vaccine is essential for the control of measles.
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.
During the 1980s, outbreaks of measles occurred among school-age children in schools with measles-vaccination levels of greater than or equal to 98% (18). Primary vaccine failure was considered the principal contributing factor in these outbreaks.
Vaccines - Measles Vaccine
Although some epidemiological studies have shown slight increases in attack rates over time after vaccination with live vaccine at 12 months of age or older, none has yet documented a significant increase. During outbreaks, observed attack rates in persons vaccinated 15 years or more before infection have been on the order of 5% or less, and calculated vaccine efficacies have generally been 90 to 95% or greater.
Since the initial recommendations for a second measles vaccination were made in 1989, no additional epidemiological evidence has emerged to suggest that waning immunity is a significant problem. Boosting of prevaccination antibody titers, when it occurs, appears to be transient (?). The major effect of the second dose appears to be in immunizing persons who failed to respond to the initial dose (i.e., persons who experienced primary vaccine failure).
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LEGAL ADVICE. THE DECISION WHETHER OR NOT TO VACCINATE IS AN IMPORTANT AND
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