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Abstract:
As a result of a large outbreak of measles, measles hemagglutination inhibition (HI) titers were measured in 465 immunized children. Titers of less than 1:4 were found in 14.6% of children immunized at 12 months of age as compared to 5.2% of those immunized at 13 months of age or later. Measles antibody titers were higher in the mothers of seronegative children who had been immunized at 11 or 12 months of age than in the mothers of seroposotive children. Measles HI titers of 1:4 or more were present in 94% of children immunized at 13 months of age or later between 1962 and 1964. The findings suggest that vaccine failure and not waning antibody accounts for the majority of titers of less than 1:4 in immunized children. Reimmunization programs should be considered for those who were immunized before 13 months of age.
Insights
Children immunized against measles before 13 months of age had lower antibody titers, suggesting vaccine failure. Reimmunization programs are recommended for this group to improve measles immunity.
Area of Science:
- Immunology
- Pediatrics
- Public Health
Background:
- Measles outbreaks necessitate evaluating vaccine effectiveness.
- Hemagglutination inhibition (HI) titers are a key measure of measles immunity.
Purpose of the Study:
- To assess measles antibody titers in immunized children during a large outbreak.
- To determine the impact of immunization age on measles immunity levels.
Main Methods:
- Measles hemagglutination inhibition (HI) titers were measured in 465 immunized children.
- Analysis compared antibody titers based on age at immunization.
Main Results:
- 14.6% of children immunized at 12 months had low titers (<1:4) versus 5.2% immunized at 13+ months.
- Children immunized earlier had lower titers, suggesting primary vaccine failure.
- Maternal antibody levels were higher in seronegative children immunized at 11-12 months.
Conclusions:
- Vaccine failure, not waning immunity, is the likely cause of low measles titers in some immunized children.
- Immunization at 13 months or later is associated with higher protective antibody levels.
- Reimmunization programs should target children vaccinated before 13 months of age.