While none of the initial Phase 3 Covid-19 vaccine trials specifically included pregnant or lactating women, the limited data with regard to safety and efficacy in this demographic were promising.

Over 20 women enrolled in the initial adult Pfizer/BioNTech vaccine trial became pregnant during the study period, and none suffered pregnancy loss or perinatal complications. A recent study reported in Forbes demonstrated that breastfed infants of vaccinated women mount Covid-19 antibodies via consumed breast milk.

As reported in Forbes by Victoria Forster, pregnant women who had been infected with SARS-CoV-2 during New York City’s coronavirus surge between March and May 2020 delivered babies who tested positive for Covid-19 antibodies. Women who had more demonstrable symptoms when infected with Covid-19 had higher levels of antibodies, as did their newborns.

Vaccinating pregnant or breastfeeding women against Covid-19 has been up for debate, as vaccines have not, to date, been studied specifically in this population.

The CDC and WHO, as well as the American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal/Fetal Medicine (SMFM) have advocated for strongly considering the importance of vaccinating pregnant women.

Pregnant women who develop acute Covid-19 infections have been considered extremely high risk for developing severe complications, including fetal loss and maternal death.

Prospective trials using the Pfizer/BioNTech Covid-19 vaccine are currently underway in 4,000 pregnant women between 6 and 8 months of their pregnancy.

A Florida woman, who is a healthcare worker, received her first dose of the Moderna Covid-19 vaccine at 36 weeks of pregnancy, and three weeks later delivered a healthy newborn girl. Samples of the newborn’s umbilical cord blood at the time of delivery demonstrated presence of Covid-19 antibodies.

As discussed by authors of the pre-print article regarding this patient, maternal transmission to the fetus of both influenza as well as TDaP (tetanus, diphtheria, pertussis) antibodies after being vaccinated during pregnancy have been shown in the past to provide some protection to newborns who are too young to be vaccinated, for up to six months. It is hopeful that Covid-19 antibody transmission will provide similar protection.

When it comes to antibodies against Covid-19, whether transmitted via breast milk or in utero via the umbilical cord, it remains unclear whether these will be sufficient to prevent acute Covid-19 infections in newborns and older infants.

While it is likely that these antibodies will provide some protection, infants and children may still merit Covid-19 vaccination, as is the case for routinely used vaccines such as the flu vaccine (given to infants ages 6 months and older) and DTaP (diphtheria, tetanus, pertussis vaccine, the first dose of the series given at age 2 months).

This week, Moderna, whose vaccine is currently approved under emergency use authorization (EUA) by the FDA for ages 18 years and older, began enrollment of children ages 6 months to 11 years, to assess dosing, safety, and efficacy of this vaccine in infants and young children.

Until results of this study, enrolling over 6,000 children, are reported, newborns born to vaccinated mothers will likely receive some degree of antibody protection from Covid-19 in their first months of life.