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The Next Frontier in Vaccines: Maternal Immunization

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The Next Frontier in Vaccines: Maternal Immunization

By Pallabi Munsi

WHY YOU SHOULD CARE

It's safe and could be an effective way to build antibodies both in pregnant women and their babies.

By Pallabi Munsi

  • Scientists are developing the first vaccines specifically for pregnant women, with the goal of improving the immunity of children in their first few weeks outside the womb, when they’re most vulnerable.  
  • If approved, these vaccines hope to target two major causes of infant mortality, the respiratory syncytial virus (RSV) and the group B streptococcus (GBS).  

Catherine and Greg Hughes were still celebrating the birth of their second child, Riley, in February 2015, when the 3-week-old started exhibiting mild, cold-like symptoms with an occasional cough. After a night during which Riley barely woke up for his usual two-hour breastfeeding, his parents took him to the hospital.

Doctors began treating Riley for pertussis, also known as whooping cough. Yet in spite of medical intervention, Riley passed away at 32 days. At the time, doctors in Australia didn’t routinely offer or recommend the whooping cough vaccine during pregnancy (they now do). As a result, babies like Riley, too young to be vaccinated, were vulnerable to the highly infectious disease.

The Hugheses are not alone in their tragedy.

According to the World Health Organization (WHO), an estimated 5.2 million children under the age of 5 died mostly from preventable and treatable causes in 2019. That includes 2.4 million newborns who died within 28 days of birth and 1.5 million who died between 1 and 11 months. Many of these deaths, experts say, could have been prevented through simple, affordable medical interventions, including immunization.

Since the 1980s, millions of pregnant women have been administered vaccines to help protect their unborn in the womb from tetanus, and, more recently, from pertussis and flu. Now researchers are beginning to design vaccines for use specifically in pregnant women to help provide immunity to children in their first weeks outside the womb, when they’re most vulnerable.

[You vaccinate] the mom to boost her immunity, and as a result, you’re actually helping to protect the infant too.

Dr. Iona Munjal, director, Pfizer Vaccine Research Unit

The first such vaccines that scientists are developing hope to target two major causes of infant mortality, respiratory syncytial virus (RSV) and group B streptococcus (GBS), as maternal immunization emerges as the next frontier of vaccine research and development. Pregnant women are able to transfer antibodies to their fetuses through the placenta, and maternal immunization piggybacks on this natural process. “[You vaccinate] the mom to boost her immunity, and as a result, you’re actually helping to protect the infant too,” says Dr. Iona Munjal, director of Pfizer’s Vaccine Research Unit.

The need for breakthroughs in this field is clear. Infants are hospitalized with RSV at rates 16 times higher than with the flu. An estimated 3 million — or 9 percent — of the 33 million annual cases in children under the age of 5 result in hospitalizations. RSV causes secretions that flood the lungs, clogging up their airways. When this happens, “they can stop breathing altogether,” says Munjal. So far though, there are no known effective antiviral treatments for infants with RSV, and the only approach currently available is used mostly only on babies born prematurely or with significant heart or lung diseases.

GBS, on the other hand, is a bacterial infection that many humans can carry in their bodies but that’s particularly dangerous in newborns and the elderly. It can lead to sepsis, pneumonia and meningitis in babies. In some wealthier nations, mothers who test positive for GBS receive intravenous antibiotics during labor to reduce the chances of passing on the bacteria to their infants. But a majority of babies with early-onset GBS are born to mothers who tested negative and the antibiotics have no impact on late-onset GBS disease, so the efficacy of this strategy is limited.

That’s why global health experts now believe that in addition to extending global vaccination programs with licensed childhood vaccines, maternal immunization may be an effective way to reduce infant illness and mortality caused by some diseases worldwide.

“It’s really exciting to see that maternal vaccines are being developed to help protect against infant diseases such as GBS and RSV,” says Catherine Hughes, who is the director of the Immunisation Foundation of Australia. “Given how common these infectious diseases can be, I think most parents would be very welcoming of these vaccines. They could make a huge difference to children’s lives.”

African American female doctor preparing a pregnant woman for vaccination

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Overall, vaccination rates in mothers are increasing — and the benefits are evident. Between 2000 and 2018, 45 countries eliminated maternal and neonatal tetanus. “I really believe that the gift of some immunity is the best gift you can give to your new baby,” says Hughes. Still, an estimated 15,000 children under the age of 5 die every day from other diseases. 

Until recently, the participation of pregnant women in clinical trials, including for vaccine candidates, was prohibited or heavily restricted. Even today, Munjal says, “doing studies on pregnant women is a big hurdle.” But the World Health Organization, the Centers for Disease Control and Prevention and other agencies now encourage and recommend vaccines for tetanus, diphtheria and pertussis for pregnant women. And the evidence to support the need for targeted interventions has only grown. “It’s really vital that the community understand just how important these lifesaving vaccines are,” says Hughes of vaccines that have been approved for use by pregnant mothers. “Nobody wants to see their newborn end up on a ventilator.”

The H1N1 virus, for instance, affected pregnant women particularly severely, says Munjal. So the vaccine for the virus was rolled out also for pregnant women — underscoring the broader benefits of immunization shots for expecting women. The COVID-19 pandemic has only added further urgency to the importance of maternal immunization, with studies suggesting pregnant women might be at increased risk from the virus.

Misinformation and vaccine skepticism are the biggest challenges to helping protect more pregnant women and infants from deadly diseases, says Hughes. Munjal also thinks misinformation is holding back global efforts to encourage maternal immunization. But, she points out, scientists and public health advocates must continue the fight to spread scientific facts and data.

A pediatrician by training, she has encountered many children with RSV in particular while walking the wards. “In certain months, practically every infant was another case of RSV infection,” Munjal says. But with each sick newborn, she says, “is a mom or dad who may have had to take a day off work or stay up all night, because they’re worried about their baby not being able to breathe.”

If the maternal vaccines currently under development are ultimately proven to be clinically safe and effective, they could help break that cycle of suffering. “If I can take that anxiety away from one person, that’s amazing,” says Munjal. The vaccines could theoretically help to prevent RSV in the nearly 120,000 infants who die from the disease each year. It’s no miracle — just the power of science.

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