New maternal vaccine options could offer extra protection in upcoming seasons.
An earlier than expected onslaught of respiratory syncytial virus (RSV) cases last spring and again this past fall strained health care 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 said the virus’ run appeared to be on the decline.
“It was a really impressive early RSV season this year,” notes Adam J. Ratner, MD, of Hassenfeld Children’s Hospital at NYU Langone in New York, New York. 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 5 and under each year in the United States. Additionally, the virus is thought to cause around 2 million outpatient visits and between 100 and 300 deaths in children aged under 5 years.1
On average, the CDC reports that there have been approximately 43.4 RSV-associated hospitalizations per 100,000 people so far in the 20222023 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 signify 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, the American Academy of Pediatrics (AAP) updated its recommendations on the use of palivizumab to prevent severe cases of RSV.
Citing a decrease in RSV infections during the COVID-19 pandemic followed by significant change in seasonal epidemiology, AAP revealed that additional doses—more than the typical 5 consecutive doses—of palivizumab may be required by provide adequate protection. There is no evidence that additional doses, or doses of palivizumab given at increased frequency, would lead to adverse effects, notes AAP.
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, which was administered to mothers late in the second trimester or third trimester of pregnancy, 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.
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 are at high risk of severe RSV-related illness, according to Pfizer.