Roughly six decades after the first attempt to develop an RSV vaccine, an independent advisory committee to the Food and Drug Administration is poised to recommend two respiratory syncytial virus shots this week.
Thus far, no RSV vaccine has been approved in the U.S.
On Tuesday, the FDA committee is evaluating Pfizer's single-dose vaccine for people ages 60 and up. If the committee votes in favor, FDA approval is likely to follow, though it could take weeks or months.
Then on Wednesday, the committee will evaluate another RSV vaccine that targets the same demographic, this one from GlaxoSmithKline.
RSV infects most people by age 2, and it is common to contract the virus multiple times throughout life. In the U.S., the virus kills more than 10,000 adults 65 or older and around 300 children under 5 every year.
RSV cases spiked dramatically in the U.S. earlier this winter, which overwhelmed children's hospitals — a reminder of the virus's threat. Since then, the pharmaceutical race to get vaccines to market has garnered extra attention.
"There’s a very clear public health need for these vaccines, and we’re going to have to see which vaccines prove themselves in terms of safety and efficacy,” said Dr. Ofer Levy, the director of the Precision Vaccines Program at Boston Children’s Hospital.
In total, 11 RSV vaccines are being actively studied in U.S. trials, according to data provided to NBC News by PATH, a nonprofit global health organization. Seven of them are for older adults, and four are designed to protect infants or children.
“This is kind of the beginning of a new era,” said Dr. Barney Graham, a senior adviser for global health equity at Morehouse School of Medicine, who previously was the deputy director of the National Institutes of Health’s Vaccine Research Center.
“I actually think all of [the vaccines] are going to work well enough to be approved, depending on the side effect profiles," he added.
According to an FDA briefing document released ahead of Tuesday's meeting, Pfizer’s data suggests its vaccine reduced the risk of RSV-related illness for older adults by 67% to 86%.
Earlier this month, data published New England Journal of Medicine showed that GSK's shot lowered the risk of symptomatic illness among older adults by 83% and of severe illness by 94%.
Both shots came with mild to moderate side effects like injection site pain, fatigue and muscle pain.
From zero options to multiple candidates
In an editorial published earlier this month in the New England Journal of Medicine, Graham described the advances that have been made since an RSV vaccine trial in the 1960s was linked to two infant deaths.
The failure stalled development for several decades. But now, Graham said, researchers have learned that RSV vaccines must target a specific protein on the virus’s surface before it changes its original shape.
“These are vaccines that are made with atomic-level precision,” he said.
Behind Pfizer’s and GSK’s vaccines, a monoclonal antibody injection from Sanofi and AstraZeneca is next in line for FDA approval. The shot, which has already been approved in Europe, is designed to protect babies from the virus. Although it is not technically a vaccine, it would serve the same purpose. The FDA began reviewing the companies’ data in January.
Pfizer has also tested a second application of its shot in pregnant people to help protect their infants from RSV. When the vaccine was administered for that purpose, the company's findings suggest it reduced the risk of severe illness in infants by 82% through their first 90 days of life, and 69% through six months. The FDA is reviewing that data and could decide in August whether to approve the shot for pregnant people.
Other notable vaccine candidates in the pipeline include a shot for older adults from Moderna, which the company has said could get submitted to the FDA by July for subsequent approval. Another candidate, from Bavarian Nordic, targets the same demographic, with phase 3 data expected by the middle of the year.
Janssen, J&J’s pharmaceutical arm, is also testing an RSV vaccine for older people. The company's phase 2 trial results, published this month, found that the shot reduced the risk of severe disease by 80% among people 65 and up.
The benefits of vaccine variety
Levy said it will be important to have multiple options.
“You don’t want all the eggs in one basket,” he said. “You don’t want to be dependent on just one manufacturing stream, that’s No. 1. No. 2, in my opinion, it’s favorable to have more than one platform.”
A vaccine platform is the technology used to spur an immune response. Having a variety on the market is ideal, because people may respond differently to shots based on their age, sex or immune status.
Graham said he eventually hopes an RSV vaccine will be approved for young kids, as well.
“If we could find things that would work and be safe in the 6-month-to-5-year-old child, to me that would kind of complete what we could do for RSV,” he said.
In serious cases, RSV infections can lead to bronchiolitis, which causes airways to become inflamed and clogged with mucus, making it difficult to breathe. If an infection travels to the lung sacs, it can result in pneumonia.
Older adults and infants are particularly vulnerable to such outcomes. For most people, however, RSV symptoms resemble a common cold, so vaccines would not be necessary for everyone, Graham said.