The US Food and Drug Administration’s independent vaccine advisers voted Thursday in favor of recommending approval of a new vaccine to protect infants from respiratory syncytial virus, known as RSV.
“This is great news for kids and moms everywhere in the US,” said Dr. David Kim, a member of the advisory committee who voted in favor of the vaccine. Kim is director of the Division of Vaccines at the Office of Infectious Disease in the US Department of Health and Human Services. “The burden of RSV disease is high, and there’s a definite need for preventive care.”
The committee considered the vaccine’s safety and effectiveness. The advisers voted unanimously that it was effective, but they were not in universal agreement about its safety, based on the data that has been collected.
“I find the data on efficacy quite compelling, in particular the high efficacy against severe RSV disease,” said Dr. Holly Janes, professor in the Vaccine and Infectious Disease Division and the Public Health Sciences Division at the Fred Hutchinson Cancer Center, who voted “yes” on the efficacy question but “no” on the safety question.
“I’m still wrestling with the totality of evidence,” she said. “I sort of wish that we could have some more discussion and more data on how to put these benefits and potential risks together.”
The approval decision now goes to the FDA. If the agency ultimately approves the vaccine, it will be the first to protect babies against RSV – a goal scientists have been working toward for decades.
The maternal vaccine is a single-dose shot would be given to a pregnant people late in pregnancy. It would trigger the development of antibodies that are passed on to the fetus and provide protection for about the first 6 months of the baby’s life.
Trials show that the vaccine, made by Pfizer, cuts the risk that infants would need to see a doctor or be admitted to the hospital with a moderate to severe infection, according to a new analysis by government regulators.
Why there’s a need for a vaccine
Last year, children’s hospitals across the country were so busy with respiratory infections that some had to set up tents or temporary beds in their parking lots to accommodate the flood of patients. Covid-19 on top of the flu and RSV challenged hospitals, but even in a typical RSV season, hospitals stay busy.
RSV is ubiquitous, and although nearly every child will get the virus before they turn 2, most children will have mild cases. RSV infections often look like a cold. For some children, though, the virus can be quite serious.
RSV is the No. 1 reason for child hospitalizations in the US. In a single year, there are about 34 million episodes of RSV-associated lower respiratory tract infections in children under the age of 5, and about 10% need to go to the hospital for treatment, studies show.
Nearly 80% of children hospitalized with RSV before age 2 had no underlying medical conditions, the FDA said in its presentation to the committee Thursday.
Once at the hospital, most kids improve with supportive care, but there is no specific drug to treat RSV. In some cases, the infection can turn into pneumonia and become deadly.
The introduction of a monoclonal antibody developed in the 1990s, palivizumab, made RSV much more survivable for infants who are vulnerable to severe illness, but only a small number of infants qualify for it.
It also comes with some challenges. It has to be given once a month, and logistics can be difficult for parents. Monoclonal antibodies can also be expensive and are not available in every country. The FDA is considering new monoclonal antibodies for infants this year.
Globally, about 64 million people get sick with RSV each year, and at least 160,000 die, according to the National Institute of Allergy and Infectious Disease. RSV causes about 1 in 28 deaths among infants ages 28 days to 6 months worldwide, studies show. But because most RSV deaths don’t happen at the hospital, that number is probably an undercount, a 2022 study found.
RSV is costly, too. Every year, the US spends more than $709.6 million on hospitalization for infants with RSV alone, studies show.
Vaccine’s protection isn’t for life
The Pfizer vaccine is 82% effective at protecting newborns from severe lower respiratory tract infections in the first three months after birth, according to an FDA analysis published Tuesday. It was 57% effective at keeping babies from having to see the doctor for an RSV infection. By about six months after birth, the vaccine was 69% effective at preventing severe disease and 51% effective at keeping them out of the doctor’s office for breathing problems.
“If the vaccine actually lives up to the data that we’ve seen today, I can guarantee that many infants and their parents will breathe easier in the coming years,” Dr. Jay Portnoy, a professor of pediatrics at Children’s Mercy Hospital, said at Thursday’s meeting.
Portnoy, who voted in favor of the vaccine, said he is grateful for the possibility that RSV case numbers could be reduced in the near future. “I’ve seen the epidemics of it for my entire career.”
Pfizer told the FDA committee Thursday that maternal vaccination could prevent up to 16,000 hospitalizations and more than 300,000 visits to the doctor due to RSV each year if the vaccine is universally applied.
However, the vaccine does not offer protection throughout the child’s life like a measles vaccine does. After about six months, it was about as effective as a placebo at keeping babies from having to see the doctor.
The safety conversation
In trials, the number of people who had reactions or serious adverse events after vaccination were balanced between the group that got the vaccine and the one that didn’t.
The most common side effects were minor and included fatigue, headache, muscle pain and pain at the injection site.
At Thursday’s advisory meeting, the committee members took two votes. They voted 14-0 that the data backs up the vaccine’s effectiveness but only 10-4 that the data supports its safety.
What led some members to vote “no” on the safety question was the slightly higher proportion of preterm birth in babies whose moms got the experimental RSV compared with those who got a placebo: 5.7% vs. 4.7%, respectively. The difference is not considered statistically significant, so it could be due to chance.
Rates of preterm births in both groups were lower than what’s reported in the general population, which is about 10%. Most infants, even when born prematurely, were delivered after 34 weeks of pregnancy, just a few weeks shy of their due dates.
Late-stage trials of a different maternal vaccine for RSV created by the drug company GSK were stopped in February over safety concerns. There was a higher risk of preterm births among mothers given the GSK RSV vaccine in the study, compared with those who got a placebo, according to a report published in the journal BMJ.
Although the GSK vaccine was not under consideration Thursday, it was something Dr. Paul Offit had in mind when he voted “yes” on the efficacy of the Pfizer vaccine but “no” on its safety.
“I do think a lot’s at stake,” said Offit, a professor of pediatrics in the Division of Infectious Diseases at the Children’s Hospital of Philadelphia. ”If you’re in any sense risking premature births with this vaccine, I think there’ll be a big price to pay, and so I guess I just don’t feel we have enough data to be reassuring.”
Dr. William Gruber, senior vice president of vaccine clinical research and development at Pfizer, told the FDA committee that there is “no definitive evidence to suggest that there in fact, is an increased risk of prematurity.”
Voting with the majority who said “yes” on both safety and effectiveness, HHS’s Kim wasn’t concerned about numbers of preterm births that were considered statistically insignificant.
“I guess when I put all the evidence together, I’m not convinced that there’s a clear causal relationship between this vaccine and preterm birth. I don’t think we can rule out chance. I don’t think we can rule out confounding by time or place,” Kim said.
“There’s never complete certainty when we’re asked to review these topics,” said committee member Dr. Arnold Monto, professor emeritus of epidemiology at the University of Michigan. “This is a disease we’ve been trying to prevent for half a century. And this is the first time we’ve had a chance to do it with a vaccine.”
Pfizer said it plans a large postmarket safety study that will use large databases of commercial claims data, including Medicaid data, to help evaluate safety endpoints – including preterm birth – in everyone who gets the vaccine.
The committee members agreed that postmarket data will be important.
“Through post-licensure data, we can have providers be able to tell their patients that they are absolutely confident that this is a safe vaccine and it will protect their infant, which, I think that was clear,” said Dr. Amanda Cohn, director of the Division of Birth Defects & Infant Disorders at the US Centers for Disease Control and Prevention’s National Center on Birth Defects and Developmental Disabilities.
There were 17 deaths in the main trial, the government’s analysis found: five in the group that got the vaccine and 12 in the group whose moms got a placebo.
The FDA agreed with Pfizer’s analysis that four of the five deaths in the immunized group were probably not related to the vaccine. With one of the deaths, a baby born very prematurely 10 days after the child’s mother was vaccinated, the agency said it couldn’t exclude the possibility that it was related to the vaccine.
One infant in the placebo group died of an RSV infection.
The only other approved RSV vaccine, made by GSK, is for older adults. Pfizer’s RSV vaccine for older adults is being considered for approval.
Many pediatricians say they are hopeful that this vaccine will be approved.
“I really am optimistic that this will make RSV less of a problem in the future,” said Dr. Alexandra Yonts, an infectious disease specialist at Children’s National in Washington, D.C. She believes that the vaccine could easily become a part of the routine care that women get late in pregnancy, similar to the TDAP vaccine, a booster that protects against tetanus, diphtheria and pertussis (whooping cough).
“Plus, the moms will get the added benefit of a little boost to their immunity, and they’ll be less likely to get that annoying cold,” Yonts said.
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Dr. Bill Muller, an infectious disease physician at Ann & Robert H. Lurie Children’s Hospital of Chicago, said anything that would decrease RSV infections would be a “welcome intervention.”
“Just decreasing the amount of disease that we see would really be an important advance in pediatric medicine,” said Muller, who is also a professor of pediatrics at the Northwestern University Feinberg School of Medicine.
“This could make a huge difference,” said Dr. Amy Edwards, associate medical director of pediatric infection control at UH Rainbow Babies and Children’s Hospital in Cleveland. The trick, she said, will lie in educating people about why they might need this vaccine.
“RSV is such an underreported illness that unless you’re one of the people who has a child that’s been affected by it or know someone in your family, I think it flies under the radar. But any pediatrician will tell you, RSV puts as many people in the hospital every year as flu does and kills as many,” Edwards said. “If you look at the protection that the vaccine provides to newborn babies, it’s tremendous, and you can ask any mom of any kid that needed to be in the ICU for RSV. They’d tell you how much they would have given to have this vaccine with they were pregnant to protect their newborn babies.
“If the mom gets vaccinated during pregnancy and babies have better outcomes, meaning fewer ICU admissions, that’s totally game-changing.”
CNN’s Brenda Goodman contributed to this report.