It is the wish of mothers everywhere to give their babies the healthiest possible start to life. It’s a feeling I remember well as I prepared to give birth to my son Homer amid an active flu and respiratory syncytial virus (RSV) season and a global pandemic—full of hope and full of fear.
The first few weeks of a baby’s life are particularly worrisome and nerve-racking for any new parent. That’s because while our little ones are quickly learning to see, grasp, and respond to our voices, it will take up to three months for parts of their still-developing immune systems to mature fully. During this time, they are particularly vulnerable to viruses and bacteria that are an everyday part of life.
While my husband and I were lucky to have our son enter this world in a clean and modern hospital and to be able to mostly “bubble” ourselves off from the outside world during those early days, not every parent is so fortunate. It is a well-established reality in global health that a person’s chance of survival is heavily influenced by the circumstances of their birth—including where they are born—but this disparity is especially pronounced in neonatal health. Each year, more than 2 million babies die in their first month of life and around 2 million more are stillborn—with 98 percent of those deaths occurring in low- and middle-income countries (LMICs). These losses reflect some of the most profound and preventable health inequities globally.
The potential of maternal immunization
To save more babies during their vulnerable first weeks of life, scientists are increasingly looking to harness the potential of the long-standing approach of maternal immunization in an entirely new way.
Pregnant women naturally pass on protective antibodies to their developing babies during pregnancy in a process known as passive immunity. As a result, vaccinating women during pregnancy can not only protect them from dangerous diseases but can also protect their newborns during their first few weeks to months of life.
Maternal immunization is not a new concept. Flu vaccines, as well as tetanus, diphtheria, and pertussis (whooping cough), or Tdap, vaccines are given to mothers worldwide as a routine part of prenatal care—I received both in my third trimester—and have proved stunningly successful. Neonatal tetanus deaths worldwide have been reduced by more than 95 percent since the late 1980s thanks, in significant part, to maternal immunization, and maternal pertussis vaccination has been shown to be 95 percent effective in preventing infant deaths from whooping cough
More nascent on the scientific front are efforts to develop vaccines designed specifically for pregnant women for the purpose of maternal immunization.
Historically, research into maternal vaccines has been limited, largely due to concerns about the ethical and safety considerations of studying and administering vaccines during pregnancy. But thanks to interest and investments from major global health research funders like the Gates Foundation and its efforts to better characterize statistical baselines for “normal” pregnancy outcomes to meaningfully enable comparative research, a small but promising pipeline of new maternal vaccines has emerged.
Harnessing maternal vaccines to combat leading causes of infant death
The first-to-market new maternal vaccine was an RSV vaccine from Pfizer, which was first approved by the US Food and Drug Administration in August 2023, making it the first and, still, the only available maternal vaccine to protect infants against RSV, a common respiratory disease that claims the lives of 100,000 children under five each year, with half of those deaths occurring before six months of age. The vaccine, which is given to pregnant women between weeks 32 to 36 of pregnancy, helps protect infants during their first six months of life.
More recently, the vaccine was recommended and then later prequalified last month by the World Health Organization, which should help support the procurement and uptake of the vaccine worldwide, particularly in LMICs, where the mortality burden of RSV is the greatest.
Beyond RSV, maternal vaccines are being advanced against two other infections that are significant drivers of infant deaths worldwide, Group B Streptococcus (GBS) and Escherichia coli. GBS bacteria, if transmitted to an infant during pregnancy or childbirth, can lead to serious and deadly conditions, including meningitis, pneumonia, or sepsis. It’s a common infection: about one in four pregnant women carry it, but the resulting health outcomes for infants are drastically different depending on where in the world one gives birth. In high-income countries, pregnant women are screened for GBS as part of routine prenatal care, and, if infected, they are given antibiotic treatments prior to delivery. In low-income countries, with less capacitated health systems, this care is less likely to occur, leading to a stark difference in health outcomes. An estimated 97 percent of infant GBS deaths are in LMICs.
But the future could look brighter. A promising maternal vaccine for GBS from Pfizer completed Phase 2 clinical trials in 2023 and received a breakthrough designation from the US Food and Drug Administration to expedite its development and review. A second vaccine candidate from MinervaX is also in Phase 2 development. Researchers estimate that maternal GBS vaccination could prevent more than 50,000 GBS-related deaths and 170,000 preterm births annually.
Similar to GBS, E. coli is a common bacterium, often transmitted from mothers to their babies during childbirth, which can cause serious illnesses, including meningitis and sepsis. Proper screening and antibiotic treatment during pregnancy can greatly reduce these risks, but for those newborns that do develop sepsis, the speed with which treatment is delivered is a key determinant of survival. The risk of death from neonatal sepsis increases by 7.6 percent every hour that treatment is delayed, underscoring the risk for infants in LMICs, who are more often born outside health facilities and far from medical care.
GHTC member the Combating Antibiotic-Resistant Bacteria Biopharmaceutical Accelerator is supporting the development of GlyProVac’s maternal E. coli vaccine, which is still in the early stages of development but, if proven effective, could one day save the lives of at-risk newborns.
Healthy beginnings, hopeful futures
As a parent, I’ve experienced the fear and feeling of helplessness that often comes with having a sick infant. You snuggle and comfort their fragile bodies, doing what you can—including vaccination when available and accessible—but often, especially in low-resource settings, there is little to do beyond monitoring, waiting, and hoping they get better. I know that if the option existed to get a few additional shots to help protect my baby during those early vulnerable weeks of life, I, and so many mothers worldwide, would joyfully jump at the opportunity.
In the years ahead, maternal immunization could play an even greater role in preventing hundreds of thousands of newborn and fetal deaths. By embracing its promise, we can help give babies everywhere a healthy beginning and a hopeful future.