Q&A: Pediatric RSV prevention tools are a ‘game changer’
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Key takeaways:
- The FDA is currently reviewing a monoclonal antibody and a maternal vaccine against respiratory syncytial virus.
- An expert is “optimistic” that they both could be used for the upcoming season to prevent RSV in young children.
The FDA recently approved two separate vaccines to prevent respiratory syncytial virus in older adults. Soon, additional RSV prevention tools may be available for pediatric patients, too.
After RSV surged in the United States last fall, FDA advisory committees examined two different approaches to preventing severe disease in children. Last month, the Vaccines and Related Biological Products Advisory Committee, or VRBPAC, voted in support of a vaccine developed by Pfizer that can protect children against RSV through maternal immunization. Additionally, last week, the Antimicrobial Drugs Advisory Committee (AMDAC) voted in agreement that the benefits of nirsevimab, a monoclonal antibody for infants made by AstraZeneca, outweighed its risks in neonates and infants born during or entering their first RSV season.
John S. Bradley, MD, medical director of infectious diseases at Rady Children's Hospital-San Diego and a former member of the AMDAC, spoke with Healio about the committees’ deliberations and when physicians can expect to use these prevention tools in practice.
Healio: What did you think about the VRBPAC deliberations on Pfizer’s vaccine?
Bradley: First of all, vaccine programs in adults have been much more difficult to implement than in pediatrics. Virtually all children see a doctor for checkups and shots. Not all pregnant women see doctors, despite its importance.
If you give the RSV vaccine to the mother, she will produce polyclonal antibodies. All of these have the ability to pass into the baby’s bloodstream through the placenta so that the baby gets protection from the mom passively. This is particularly effective during the last month of pregnancy — the antibody will be passed so that by the time the baby is born he or she will be protected. This amount of antibody is not quite as high as the new monoclonal antibody by AstraZeneca given directly to infants, but it is better than nothing. The challenge here is getting the mom immunized.
Healio: What do you think of the AMDAC deliberations on AstraZeneca’s monoclonal antibody?
Bradley: To be clear, this is not a vaccine, it is a humanized monoclonal antibody. This is the same as the antibodies that the body creates to protect itself after it has been exposed to a virus or to bacteria. There are monoclonals for many illnesses, including cancer. This type of medicine has been around for a long time. In fact, there are already monoclonal antibody shots against RSV, such as Synagis (palivizumab, Sobi). Worldwide, we use Synagis today to prevent RSV infections in children with underlying diseases, such as lung disease or congenital heart disease. The caveat here is that it is short-acting, so doctors need to give injections to the baby every month during RSV season. Something additional to note is that Synagis is not a treatment for RSV — Synagis and other monoclonal antibody shots are preventive medicine.
The difference here is that the AstraZeneca monoclonal antibody shot that is currently under deliberation with the FDA can be given to healthy infants, not just those with underlying diseases. This is a game changer because it will prevent infants across the board from becoming very sick with RSV and will reduce the number of children needing to be hospitalized for RSV infection. For the parents, this will significantly relieve anxiety.
Another major change is that AstraZeneca has tweaked the antibody itself so that infants won’t need shots every month; they’ll only need it every 5 months. This means that they’ll really only need it once a year, at the start of RSV season. Another thing to note is that while the shot does not prevent infection, it significantly decreases the severity of the infection. They won’t get nearly as sick and they won't get hospitalized nearly as often. Even though the shot just contains an antibody, if a baby gets infected, he/she will still be able to create their own, lasting immune response to prevent future infections. In this way, it’s like a vaccine as the end result is that there’s an antibody to protect the child.
By some estimates, there will be 3 million to 4 million babies treated with this new shot each year; nearly every newborn baby will receive it. This is a huge advance for pediatric health. For context, we had almost 1,000 hospitalizations with RSV last year. This shot will decrease that by 50% to 75%, so for the next RSV respiratory season, I expect we’ll get a couple hundred hospitalized babies, rather than 1,000. It will also reduce the number of visits to the pediatrician for RSV by 50% to 75%.
I used to be a member of AMDAC, and I can say that the FDA usually goes with what the committee recommends. Something very unique is that I’ve never seen such unanimity in their decision-making before as they had with this recommendation. The FDA will likely approve it within the next few weeks, but we don’t know if the FDA will approve everything that AstraZeneca has asked for. Although we don’t know whether we’ll have it for this RSV season, I’m very optimistic.
There are very few times when every healthy child will get something new. Vaccines are generally pretty widely accepted. This will be the first time that a monoclonal antibody will be given to every newborn baby. People will think of it as a vaccine, but it only protects you for one season. It is important that we get the word out to parents that it’s not a vaccine. It’s only 5 months protection right now.
Healio: Are there major differences between the Pfizer vaccine and the maternal RSV vaccine that GSK stopped testing based on a safety assessment?
Bradley: The major difference is that the GSK vaccine had safety issues and the Pfizer vaccine did not. We don’t know why this is the case.
Healio: If the Pfizer vaccine is approved, who would take the lead in vaccinating pregnant people?
Bradley: It would most likely be OBGYNs or whoever takes care of pregnant women. That is who will be charged to educate every pregnant woman about the vaccine.
Healio: Would it be given to pregnant people just during cold and flu season or year-round?
Bradley: The most antibody protection people typically get occurs within a month or two of when the injection is administered, but these vaccines grant long-lasting protection. Pfizer may ask the FDA to immunize all pregnant women. However, the FDA may only approve vaccine to immunize women between specific months of the year, based on the circulation of the RSV virus. It tends to take 3 weeks to 4 weeks for the shot to take effect, producing sufficient antibody to protect the baby.
Healio: What is in the works to protect children aged older than 6 months from RSV?
Bradley: The RSV monoclonal antibody shot is recommended to be approved for all children for the first year of life, which is important because the hospitalization rate is highest during the first year of life. Once a child is bigger, their rib cage becomes stiffer. A 1-and-a-half-year-old to a 2-year-old child can open airways in their lungs that a 6-month-old can’t. There’s not as critical of a need for kids in the second year of life. However, if a child is at high risk for severe RSV pneumonia due to ongoing underlying chronic lung disease or from congenital heart disease, which makes their lungs more stiff compared with normal lungs, they still have a high rate of hospitalization during their second year of life. To manage these cases, AstraZeneca asked for approval for nirsevimab for second-year children at high risk.
The RSV vaccine that was approved for mothers is also currently being tested in babies. In the future, RSV vaccines are likely to be given just like pertussis vaccines at 2, 4 and 6 months of age, but we don’t know when it will be approved.
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