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RSV surges early in 2022, but appears to make early retreat

New maternal vaccine options could offer extra protection in upcoming seasons.

An earlier than expected onslaught of respiratory syncytial virus (RSV) cases this fall strained healthcare resources across the country, increasing worries about the availability of hospital beds for the remainder of the winter cold and flu season.

By mid-winter though, when RSV cases usually hit their peak, experts say the virus’ run appeared to be on the decline.

“It was a really impressive early RSV season this year,” recounts Adam J. Ratner, MD, of Hassenfeld Children’s Hospital at NYU Langone.

Ratner says pediatric hospital beds were certainly in short supply throughout the fall—much earlier than usual—as RSV cases surged. The peak seems to have passed, at least in New York, he says.

While different areas of the country have seen RSV viral surges come and go in waves, nationally it seems that the virus made an early appearance almost everywhere in 2022.

Typically, RSV leads to between 58,000 and 80,000 hospitalizations in children aged 5 years and under each year in the U.S. Additionally, the virus is usually blamed for around 2 million outpatient visits and between 100 and 300 deaths in children aged under 5 years.1

On average, the Centers for Disease Control and Prevention (CDC) reveals that there were around 43.4 RSV-associated hospitalizations per 100,000 people so far in the 2022-2023 season.2 Typically, the bulk of RSV-associated hospitalizations are in children aged under 1 year old, according to previous studies.3

It’s too early to close the curtain on the RSV season, but weekly case totals reported by the CDC reveal a significant jump in early cases over previous years.

For example, the CDC tallied nearly 42,000 cases of RSV between October and November 2021. In contrast, there were more than 126,000 cases detected between October and November 2022. However, the data also shows that while RSV cases began rising earlier in the year, a decline in cases started by early December 2022—more than a month earlier than the previous year.4

This earlier than normal peak spurred public health experts to offer new guidance on managing RSV, especially in high-risk infants.

In November 2022, the American Academy of Pediatrics (AAP) updated its recommendations on the use of the monoclonal antibody treatment palivizumab as a tool to prevent severe cases of RSV.5

Citing a decrease in RSV infections during the COVID-19 pandemic followed by significant change in seasonal epidemiology, the AAP revealed that additional doses—more than the typical 5 consecutive doses—of palivizumab may be required to provide adequate protection. There is no evidence that additional doses, or doses of palivizumab given at increased frequency would lead to adverse effects, notes the AAP.5

Research continues also into a number of immunization options that could help decrease the RSV burden in future seasons. Ratner says there are several promising late-stage clinical trials, and Pfizer announced in late 2022 that its bivalent RSV prefusion vaccine candidate, RSVpreF or PF-06928316, offered promising protection to infants when administered to expectant mothers in late pregnancy. According to data from the clinical trials, the vaccine was administered to mothers late in the second trimester or third trimester of pregnancy. The vaccine was found to be almost 82% effective in preventing severe respiratory infections from RSV in infants from birth to 3 months of age. Protection continued through the first 6 months of life, according to trial data, demonstrating about 70% efficacy.6

Pfizer is currently seeking approval to make RSVpreF/PF-06928316 the first maternal vaccine to help prevent severe RSV-related illness in infants. Another formulation of the vaccine has also been developed for use in older adults who at high risk of severe RSV-related illness, according to Pfizer.6

Reference

1. RSV research and surveillance. Centers for Disease Control and Prevention. Accessed January 15, 2023. https://www.cdc.gov/rsv/research/index.html.

2. RSV-NET interactive dashboard. Centers for Disease Control and Prevention. Accessed January 15, 2023. https://www.cdc.gov/rsv/research/rsv-net/dashboard.html.

3. Zheng, Z, Warren, JL, Shapiro, ED, et al. Estimated incidence of respiratory hospitalizations attributable to RSV infections across age and socioeconomic groups. Pneumonia. 2022;14(6). doi:10.1186/s41479-022-00098-x

4. RSV numerator data for the US Centers for Disease Control and Prevention. Accessed January 15, 2023. https://www.cdc.gov/surveillance/nrevss/images/trend_images/RSV14Num_Nat.htm.

5. Updated guidance: use of palivizumab prophylaxis to prevent hospitalization from severe respiratory syncytial virus infection during the 2022-2023 RSV season. American Academy of Pediatrics. Accessed January 10, 2023. https://www.aap.org/en/pages/2019-novel-coronavirus-covid-19-infections/clinical-guidance/interim-guidance-for-use-of-palivizumab-prophylaxis-to-prevent-hospitalization/.

6. Pfizer announces positive top-line data of phase 3 global maternal immunization trial for its bivalent respiratory syncytial virus (RSV) vaccine candidate. Pfizer. Accessed January 10, 2023. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-announces-positive-top-line-data-phase-3-global.