Researchers say maternal protection against measles may fade months before routine vaccination begins, prompting questions about whether some infants need earlier protection.
A study presented at IDWeek suggests that most babies lose measurable measles antibodies by the time they are 6 months old, a finding that could reopen debate over when protection against the virus should begin. C. Buddy Creech, a paediatric infectious diseases specialist involved in the research, said the results indicate that many infants are no longer covered by maternal antibodies well before the age at which routine vaccination starts in the United States.
The current American schedule recommends the first dose of measles, mumps and rubella vaccine at 12 to 15 months, followed by a second dose at 4 to 6 years, according to the Centres for Disease Control and Prevention. The CDC and the American Academy of Pediatrics both allow infants as young as 6 months to receive an early dose before international travel or during a community outbreak, but children vaccinated that young still need to receive the standard two-dose series later on.
Creech said the timing of the schedule dates back to a period when more mothers had natural immunity from past measles infection, which generally passed more antibodies to infants. Today, he said, most mothers in the United States are protected through vaccination, and that appears to leave babies with lower antibody levels earlier in life. Speaking to Healio, he said older and newer data alike suggest antibody levels have dropped below protective levels by 6 months of age.
In the study, researchers analysed leftover blood samples from 92 mother-infant pairs who had taken part in COVID-19 vaccine studies and measured neutralising antibodies at birth, 2 months and 6 months against the vaccine strain and two common wild-type strains. Antibody levels fell sharply over the first six months of life, and by 6 months they were below detectable levels for all three measles viruses. For the vaccine strain, the proportion of seropositive infants fell from 96.7% at birth to 8.7% at 6 months, while similar declines were seen for the B3 and D8 strains. Creech said the findings raise practical questions for paediatricians working in areas with outbreaks, especially when infants are in daycare, travel frequently or live in undervaccinated communities.
Public health officials say measles remains a major concern because it spreads easily and vaccination is the main line of defence. The CDC says two doses of MMR are about 97% effective at preventing measles, and the vaccine is central to outbreak control and routine childhood immunisation. Creech said the next step is to study whether infants vaccinated at 9 months, the age recommended by the World Health Organisation in countries where infection risk is high in the first year of life, develop durable protection. He said the broader question is whether measles elimination can still be assumed and, if not, how early vaccination should begin to protect the youngest children.
Disclaimer: This content is for informational purposes only and is not intended to be a substitute for professional medical judgment, advice, diagnosis, or treatment.
