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Measles vaccine efficacy: influence of age at vaccination vs. duration of time since vaccination
Abstract:
To evaluate the recent decision of the Advisory Committee on Immunization Practice to increase the recommended age for initial measles vaccination from 12 to 15 months, we carried out a case control study of vaccine failure in a recent measles epidemic. Compared to children vaccinated at ages 15 months or older, we found an increased risk of vaccine failure among those vaccinated at 12 to 14 months (relative risk = 19.2, 95% confidence interval = 4.6 to 80.1). In order to sort out the influence of age at vaccination from elapsed time since vaccination, we subjected the data to discriminant analysis. Age at vaccination subsumed all of the effect of duration of time since vaccination. Thus, we find no evidence of waning immunity over time.
Insights
Children vaccinated for measles between 12-14 months showed a significantly higher risk of vaccine failure. This study supports delaying the initial measles vaccine to 15 months or older for better protection.
Area of Science:
- Pediatrics
- Immunology
- Epidemiology
Background:
- The Advisory Committee on Immunization Practices (ACIP) revised guidelines for measles vaccination timing.
- Recent measles outbreaks prompted re-evaluation of vaccine efficacy at different ages.
Purpose of the Study:
- To assess the impact of the revised measles vaccination age recommendation.
- To evaluate measles vaccine failure rates based on age at initial vaccination.
Main Methods:
- A case-control study design was employed during a recent measles epidemic.
- Discriminant analysis was used to differentiate the effects of age at vaccination versus time elapsed since vaccination.
Main Results:
- Vaccine failure was significantly higher in children initially vaccinated between 12-14 months compared to those vaccinated at 15 months or older (Relative Risk = 19.2).
- Age at vaccination was the primary factor influencing vaccine failure, not the time elapsed since vaccination.
- No evidence of waning immunity over time was detected.
Conclusions:
- The findings support the ACIP's decision to recommend measles vaccination at 15 months or older.
- Vaccinating at an earlier age (12-14 months) is associated with a substantially increased risk of measles vaccine failure.
- Immune protection from the measles vaccine appears durable, with age at vaccination being the critical factor.