As RSV cases continue to rise, experts warn that the virus is spreading at an usually high rate—we’re already much further ahead in case numbers than is typically expected for this time of year. Some estimates show that 71% of the country’s 40,000 pediatric hospital beds are currently filled, the highest rate in 2 years, ABC News reports. The RSV surge has parents of young infants everywhere understandably worried. But two new RSV shots are under review that may help prevent serious illness in the coming seasons—the Pfizer RSV vaccine, which is to be offered in pregnancy, and a monoclonal antibody therapy, nirsevimab, which could be offered to infants going through their first or second RSV season.

Respiratory syncytial virus, or RSV, is a common childhood virus that nearly every child will have come into contact with by age 2, but it can be especially severe for infants under 12 months and older adults, especially those with pre-existing conditions. The virus is the most common cause of the lung infection bronchiolitis and pneumonia in children under 1 in the US. More than 58,000 children under 5 are hospitalized due to RSV each year, according to the CDC.

RSV cases surge, but vaccines are in development

The 2022 RSV season seems to be especially severe due to several viruses all affecting kids at the same time, one of which is flu. “We’re seeing the co-circulation of four or five viruses that are not unusual in the sense that they’re not rare,” said Mark Kline, a pediatric infectious-disease specialist at Children’s Hospital New Orleans to The Wall Street Journal. “It’s just a viral petri dish out there right now,” he added.

Though RSV vaccine development has been attempted for 50 years,¹ no shot currently exists for the population at large. Some pre-term infants who are at higher risk for severe disease from RSV may be eligible for a monthly injection of a monoclonal antibody treatment known as palivizumab during RSV season, but just 2% of babies² are able to get those shots.

Pfizer’s RSV vaccine boasts a strong efficacy and safety profile

Results from Pfizer’s Phase 3 clinical trial for their maternal RSV vaccine were released this week, and they’re looking promising.

In a study of approximately 7,400 pregnant women, who were randomized to receive either a 1-shot dose of the Pfizer RSV vaccine or a placebo during the late second or early third trimester, researchers saw a vaccine efficacy rate of 81.8% against severe disease from RSV in infants from birth through the first 90 days of life. Results also showed 69.4% efficacy against severe disease through the infants’ first six months of life. The vaccine was well-tolerated with no safety concerns for pregnant women or newborns.

“Every year we see high levels of RSV cases among babies in the U.S. with some regions reporting hospital admission rates higher than normal this year,” said Eric A.F. Simões, M.D., Clinical Professor, Pediatrics-Infectious Diseases, University of Colorado School of Medicine and Children’s Hospital Colorado, Aurora, in a press release. “A maternal vaccine with high efficacy that can help protect infants from birth could substantially reduce the burden of severe RSV among newborns through six months of age, and, if approved by regulatory authorities, will likely have a significant impact on disease in the U.S. and globally.”

Pfizer plans to submit a request for authorization to the FDA by the end of 2022. If approved, it would be the first maternal vaccine available to prevent severe RSV in infants under 6 months.

A new RSV vaccine-like therapy could soon be available for infants

A new monoclonal antibody therapy offered to babies directly could also be widely available as soon as next year—and may be recommended for all infants under 8 months, as well as any babies born during peak RSV season (typically November through March).

The vaccine-like therapy, known as nirsevimab, developed by Sanofi and AstraZeneca, has been studied in clinical trials on more than 3,000 infants, and has a high efficacy and safety profile.

Offered as a one-time injection, the treatment was shown in trials to be 76% to 79% effective against medically attended illness, hospitalization and very severe RSV, notes AAP. Side effects including pain at the injection site, rash and fever were uncommon and similar to placebo, and there were no serious adverse reactions reported.

Monoclonal antibodies work by neutralizing the virus and suppressing viral replication. They can offer babies passive immunity against RSV infection that’s found to be more effective than giving the mother an RSV vaccine during pregnancy.

The CDC’s Advisory Committee on Immunization Practices (ACIP) will continue to review trial data in February 2023, and if the FDA authorizes the treatment, could vote in June on its usage, meaning it would hopefully be available before the start of the 2023 RSV season.

ACIP will also determine who will be eligible for the treatment, and whether that will include all children entering their first or second RSV season. (Children under 24 months entering their second RSV season are still susceptible to severe disease.)

For now, prevention is key

In the meantime, RSV prevention is crucial in reducing lung problems later in life, says Octavio Ramilo of Nationwide Children’s Hospital, The Ohio State University College of Medicine, in The Lancet. ³

If you have children under 12 months during prime RSV season, you may want to take extra precautions. That looks like good hand-washing hygiene and not being in crowded situations with a young baby, he notes. The virus spreads through respiratory droplets from coughing and sneezing, so regularly cleaning shared toys and wiping down surfaces can go a long way in RSV prevention.

A flu shot can also help prevent severe illness that might stem from co-infection—and are available for infants over 6 months.

“We are strongly encouraging parents, particularly with young children, to have their children immunized with influenza soon,” says Larry Kociolek, the medical director of infection, prevention and control at Ann & Robert H. Lurie Children’s Hospital of Chicago, to The Wall Street Journal, noting that the past two flu seasons were mild and many kids may not have had sufficient exposure. The AAP recommends kids get their flu shot before Halloween this year, but stresses that it’s not too late to schedule it for November, either.

References

1. Griffin MP, Yuan Y, Takas T, Domachowske JB, Madhi SA, Manzoni P, Simões EA, Esser MT, Khan AA, Dubovsky F, Villafana T. Single-dose nirsevimab for prevention of RSV in preterm infants. New England Journal of Medicine. 2020 Jul 30;383(5):415-25.

2. Griffin MP, Yuan Y, Takas T, Domachowske JB, Madhi SA, Manzoni P, Simões EA, Esser MT, Khan AA, Dubovsky F, Villafana T. Single-dose nirsevimab for prevention of RSV in preterm infants. New England Journal of Medicine. 2020 Jul 30;383(5):415-25.

3. Venkatesan P. Nirsevimab: a promising therapy for RSV. The Lancet Microbe. 2022 May 1;3(5):e335.

Additional sources

Rodriguez-Fernandez R, Mejias A, Ramilo O. Monoclonal Antibodies for Prevention of Respiratory Syncytial Virus Infection. Pediatr Infect Dis J. 2021;40(5S):S35-S39. doi:10.1097/INF.0000000000003121

A version of this story was originally published on Oct. 21, 2022. It has been updated.

Source(s)

1
Griffin MP, Yuan Y, Takas T, Domachowske JB, Madhi SA, Manzoni P, Simões EA, Esser MT, Khan AA, Dubovsky F, Villafana T. Single-dose nirsevimab for prevention of RSV in preterm infants. New England Journal of Medicine. 2020 Jul 30;383(5):415-25.
2
Griffin MP, Yuan Y, Takas T, Domachowske JB, Madhi SA, Manzoni P, Simões EA, Esser MT, Khan AA, Dubovsky F, Villafana T. Single-dose nirsevimab for prevention of RSV in preterm infants. New England Journal of Medicine. 2020 Jul 30;383(5):415-25.
3
Venkatesan P. Nirsevimab: a promising therapy for RSV. The Lancet Microbe. 2022 May 1;3(5):e335