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A retrospective analysis presented at IDWeek 2026 this month in Washington, D.C., suggests that infants’ maternal protection against measles may decline much earlier than previously believed, leaving many babies susceptible to infection months before their first measles, mumps, and rubella (MMR) vaccination, which is recommended at age 12–15 months. As reported in meeting coverage from MedPage Today, researchers analyzed measles antibody levels in maternal-infant pairs and found that although infants had higher neutralizing antibody concentrations than their mothers at birth, those levels declined rapidly. By age 6 months, median antibody concentrations had fallen below the threshold associated with protection against the 3 measles strains studied. At 6 months, only 8.7%–19.6% of infants remained seropositive, depending on the strain. The findings raise questions about the optimal timing of MMR vaccination. However, earlier vaccination involves trade-offs, according to the post. A previous meta-analysis found vaccine effectiveness of 51% when administered at 6 months versus vaccine effectiveness of 83% at 9 months. Researchers suggested that further investigation might consider vaccination at 9–10 months, along with potentially accelerating the second dose, which is recommended at 4–6 years, according to the American Academy of Pediatrics.
Unfortunate trend: Meanwhile, the Johns Hopkins Bloomberg School of Public Health U.S. Measles Tracker has reported 4,730 measles cases this year through October 23, 2026. And some of these cases are showing up in urgent care centers. In November, international health officials will meet to determine if the United States and Mexico have lost their measles-free status.