From the Journals

Acquired MMR immunity doesn’t last to age 1 year



Most infants are vulnerable to measles, mumps, and rubella viruses between the disappearance of antibodies acquired during gestation and their first MMR vaccination, according to results of a study in Vaccine.

vaccine toddler Yarinca/istockphoto

María José Cilleruelo, PhD, of Hospital Universitario Puerta de Hierro in Majadahonda, Spain, and colleagues showed that, although most infants acquire some protective antibodies against MMR from their mothers during gestation, most have lost this protection as early as 3 months of age. This single-center, observational, prospective study was conducted between October 2013 and December 2014, and it began with 146 mother-child pairs, with 99 remaining in follow-up at 3 months, 77 at 6 months, 63 at 9 months, and 30 at 12 months. For measles, 88% of newborns were seropositive, but only 19% were at 3 months; for mumps, 70% of newborns were seropositive, but only 11% were at 3 months; and for rubella, 91% of newborns were seropositive, but only 13% were at 3 months. No infants were seropositive for mumps or rubella at 9 months, and only 2% were for measles. No infants were seropositive for any of these viruses by 12 months of age.

The investigators noted that, given Spain (where the study was conducted) is a country that gives the first MMR vaccine at 12 months of life, these declining titers can leave most infants vulnerable to those viruses before then.

“We suggest that it may be worth considering administering the first dose of MMR vaccine before 12 months of age,” the investigators concluded, although they advised studies be undertaken into the efficacy and safety of administration of that vaccine in infants younger than 12 months. They noted that the biggest limitation of this study was the high percentage of loss to follow-up, which limited the statistical power to make comparisons.

The study was funded by the Fondo de Investigación Sanitaria, and one of the authors was funded by CIBER de Epidemiología y Salud Pública. The authors declared that there are no conflicts of interest.

SOURCE: Cilleruelo MJ et al. Vaccine. 2019;37:4164-71.

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