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Earlier first-dose measles vaccination increased infection risk
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Children receiving a two-dose measles vaccination have an increased risk for infection when the first-dose is received at age 12 to 13 months compared with older than 15 months, according to recent study findings published in Pediatrics.
The matched case-control study included 102 cases (two doses) and 510 controls aged 5 to 17 years.
Researchers found that 89% of the cases were in patients aged 13 to 17 years. Patients who received the first dose at age 12 to 13 months had a six times increased (95% CI, 1.33-29.3) risk outside of the outbreak schools compared with patients who received the first dose when they were older than 15 months. In the pooled estimate, which included patients from the outbreak school and outside of that school, patients who received the first dose at age 12 to 13 months had a 5.2 times increased (95% CI, 1.91-14.3) risk compared with patients who received the first dose when they were older than 15 months.
“Although unvaccinated people should remain the prime target for measles vaccination, the unexpected vulnerability we have identified in twice-vaccinated people could ultimately lead to failed measles elimination efforts,” the researchers wrote. “If the effect of early vaccination permanently alters the ability to respond to subsequent doses, even adding a third or fourth dose may not provide long-lasting protection. Therefore, it is critical to understand the mechanisms of primary vaccine failure or loss of vaccine protection that our findings may signal.”
Disclosure: See study for a full list of disclosures.
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