This Could Be an RSV Season Like No Other, in a Good Way

7 min read

Oct. 10, 2023 – Any parent whose baby has been hospitalized will never forget the emotions, sights, and sounds experienced while at their child’s bedside. 

The number of parents who go through that may dramatically drop forever, and this year, respiratory syncytial virus (RSV) may end its run of at least 15 years as the top cause of hospitalization among infants.

For the first time, two preventive treatments are available that dramatically reduce the risk of severe RSV. One is a maternal RSV vaccine given toward the end of pregnancy, and a second option is a shot of protective antibodies given to babies as early as the first week of life. Both are about 80% effective at preventing severe complications from RSV.

Medical providers and public health experts are hopeful there will be strong acceptance of the maternal RSV vaccine. The maternal vaccine works just as well and is just as safe as the monoclonal antibody shot that can be given to infants, but is more available and is less than half the cost. 

Jessica Ehrig, MD, a maternal fetal medicine specialist in central Texas, wishes the option had been available when she was pregnant with her first child 8 years ago because it may have prevented her daughter’s stay in the pediatric intensive care unit with RSV. As a doctor, she knew just how dangerous the illness was when she saw that her daughter’s blood oxygen level was in the 80% range as they rode in the ambulance to the hospital. A child’s normal blood oxygen level is 93% to 97%.

“I hope no momma has to be there watching their baby be in distress,” she said. “That terror and that experience – I would have done anything to prevent that.”

About 2 of every 100 babies born in the U.S. are hospitalized due to RSV within the first year of life. It’s so common that most people know someone whose child had a severe case, or perhaps they recall the most stressful days of their own parenthood at their baby’s bedside in the hospital.

The new maternal RSV vaccine is 82% effective at preventing severe complications from RSV within the first 3 months of life, and remained 69% effective at the 6-month point, according to data from the FDA. In August, the FDA approved the shot to be given between weeks 32 and 36 of pregnancy. CDC guidelines say it should be given from September through January, when RSV peaks.

RSV can lead to a condition called bronchiolitis, which causes the small airways in the lungs to swell and results in wheezing and coughing that is exhausting. Babies who are hospitalized may need fluids and a tube guided into the windpipe to help them breathe.

So far this season, RSV detections are ticking up, but the rate is far from last season’s early onslaught that was part of the “tripledemic” of respiratory illnesses. As of the week ending Sept. 30, there were about 900 cases of RSV reported to the CDC nationwide. At the same time last year, there were nearly 6,000 cases. Any RSV case count reductions so far this year are unlikely to be due to the new medicines, since they are just now becoming available.

Whether it’s a big RSV season or a typical one, RSV “is by the far the most common reason to be in the hospital the first few months of your life,” said Kevin Ault, MD, who serves on the Immunization Working Group of the American College of Obstetricians and Gynecologists. The professional group immediately announced it “unequivocally supports” the recommendation made by the CDC on Sept. 22 that all pregnant people get the maternal RSV vaccine if they are midway through their third trimester during RSV season.

Early Demand Is Strong

Despite a rising rate of vaccine hesitancy nationwide, there are some signs of potentially strong interest in the new maternal RSV vaccine. 

“The local pharmacies in town have it, and they’re seeing increasing demand with it,” said Ehrig, the maternal fetal medicine director at Baylor Scott & White Health Memorial Hospital in Temple, TX. “They’re running out and having to place larger orders. I think they were hesitant as to how much to order at first, but it seems like most moms are interested.”

Ehrig and Ault have both had pregnant patients request the vaccine already.

“I think uptake is going to be pretty good,” said Ault, chair of the Department of Obstetrics and Gynecology at Western Michigan University Homer Stryker MD School of Medicine in Kalamazoo. “There’s a very similar strategy for whooping cough, or pertussis. That strategy has worked amazingly well.”

The whooping cough vaccine, included in the shot known as Tdap, was recommended for all pregnant people starting in 1996 by the same CDC advisory group that just recently added the maternal RSV vaccine to its recommended list. The two are similar because they are given during pregnancy and can protect from disease right at birth.

“The strategy is we give Mom an injection, the mom makes antibodies, the antibodies go through the placenta and go to the fetus, and then they’re born with their protection,” Ault explained.

Before the Tdap vaccine, about 200,000 cases of whooping cough occurred in the U.S. annually. That number dropped to 5,000 cases in 2020, when just over half of pregnant people got the Tdap shot, according the Mayo Clinic.

The addition of the maternal RSV shot now makes four recommended vaccines for pregnant people: Tdap, flu, COVID-19, and RSV. Infectious diseases professor William Schaffner, MD, of Vanderbilt University School of Medicine in Nashville, is anxiously watching to see whether the new maternal RSV vaccine will be immune to the nation’s growing vaccine hesitancy.

“I would be concerned about that, and I hope that I’m wrong,” he said. “The early accepters – the people who are out there wanting to get this vaccine – I hope they are thought-leaders in their communities, in their local group of friends, and among pregnant people who talk to each other and share experiences.” 

Recent survey data shows that Tdap vaccination rates have remained relatively steady in recent years, while flu and COVID shot acceptance has varied.

During the 2022-2023 season:

  • 55% of pregnant people reported getting a Tdap shot, similar to 57% of pregnant people who said they got it during the 2019-2020 season.
  • 47% of pregnant people reported getting a flu shot, down from 61% during the 2019-2020 season, according to the same Tdap survey data.
  • 27% of pregnant people said they got the latest COVID-19 booster shot, and that rate fell to 16% during the summer of 2023.

“In my patient population, patients that are anti-COVID vaccine are actually more interested in getting the RSV vaccine,” Ehrig said. “They’ve seen babies of friends or family members who had it, or their own baby from a prior pregnancy had it and they want to try to prevent that for their unborn child.”

Not One, But Two Safe Options

In its approval, the FDA noted that the new maternal RSV vaccine clinical trials included some potentially elevated rates of preterm births and of a serious type of high blood pressure during pregnancy called preeclampsia. 

Both Ault, who temporarily sat on a FDA advisory committee that reviewed some of the maternal RSV data in May, and Ehrig said that a close look at the clinical data for those potential risks does not raise any safety flags for them. Ehrig said the preeclampsia rate was actually below that of the general population, and elevated rates of preterm births mainly occurred in countries with prenatal care that is not equal to the level of care in the U.S.

The protection from the vaccine, which is made by Pfizer under the brand name Abrysvo, lasts about one season. For mothers who don’t get the vaccine during pregnancy, there is another new protection option that can be given as a shot to a baby as early as within the first week of life and is approved for all babies up to 8 months of age. The shot for babies contains monoclonal antibodies and is about as effective as the maternal vaccine. Some high-risk babies up to 19 months old will also be able to get the monoclonal antibody shot.

“They’re both giving the same thing to babies, which we call passive immunity,” Ehrig said. “The baby doesn’t have to make its own antibodies because we’re giving it antibodies. Either from Mom or from monoclonal antibodies, essentially they both work the same way as far as protecting babies.”

But most providers are hearing there will be a limited supply of the monoclonal antibody medicine, at least for this season, so maternal vaccination will be an important option since there won’t be enough monoclonal antibody shots to go around. For people who have to pay out of pocket, the monoclonal antibody treatment costs $495, while the maternal RSV vaccine costs $295, according to the CDC

Most private insurers will cover the costs of the maternal RSV vaccine, and options exist for those without insurance.

In addition to the potentially high cost, another concern raised in the medical and public health communities is that having one option that occurs before birth and one that occurs after could challenge already difficult lines of communication between prenatal care providers and pediatricians. 

Add vaccine hesitancy to the list of challenges for these breakthrough RSV medicines, and the communities of prenatal care, pediatrics, infectious diseases, and public health are all anxiously hoping that in this RSV season, children’s hospitals nationwide will report the most unused beds in history.

Correction: An earlier version of this story incorrectly sat on a CDC advisory committee. It was an FDA committee.