One in five Philadelphia newborns is not protected from measles, CHOP-Penn study finds

One in five babies born in Philadelphia likely has no immunity against measles, a new study has found, raising the child’s risk of catching a disease that can lead to hospitalization and death.

That’s because their mothers had no antibodies in their blood to pass on during pregnancy, according to an analysis of maternal blood samples at two city hospitals. As a result, they were unable to pass along any protection against the disease to their newborns, leaving the children vulnerable until getting their first dose of vaccine at age 12 months.

The study authors, from Children’s Hospital of Philadelphia and the University of Pennsylvania, stopped short of making a firm recommendation to address the problem, but they wrote that in the event of a measles outbreak, it might make sense to vaccinate these unprotected children at a younger-than-usual age.

At the very least, public health officials should identify the children at risk, said lead author Dustin D. Flannery, a neonatologist at CHOP.

“The implication is that one in five newborns in Philadelphia are likely born without any measles immunity,” he said. “In the setting of an outbreak, that could be critically important to identify who those newborns are.”

Since the start of the COVID-19 pandemic, fewer children have gotten their routine vaccinations for measles and other once-common diseases, leading physicians to warn that more outbreaks are likely.

One just happened in Ohio, striking 85 children, of whom 80 had not been vaccinated and 36 were so sick that they were hospitalized. The highly contagious disease typically starts with a cough and fever, followed by a skin rash. In severe cases, measles can cause swelling in the brain and death. None of children recently sickened in Ohio died.

The new CHOP-Penn study, published in JAMA, was based on blood samples from 513 patients who delivered babies at Pennsylvania Hospital and the Hospital of the University of Pennsylvania from April to October 2021.

Of that total, 410 had detectable levels of measles antibodies in their blood — some of which would’ve been passed on to the fetus through the placenta, affording a degree of protection for up to 6 months.

But 103 of the pregnant patients had no detectable levels of measles antibodies in their blood, meaning they had none to pass on to their offspring.

The findings echoed the results of an earlier study in New York, in which 23% of pregnant women lacked antibodies to measles.

In both studies, the lack of antibodies did not necessarily mean that the pregnant patients had not been vaccinated against the disease, Flannery said. Most of them likely had been vaccinated as children, yet their antibody levels had waned since then, he said. If they were infected themselves, their immune systems likely still have the ability to respond by making new antibodies.

But without any antibodies circulating in the blood during pregnancy, their children would be vulnerable after birth.