RSV prevention strategy 2
Universal RSV vaccination of pregnant persons from September through January
The RSVpreF vaccine (Abryvso, Pfizer) is approved by the FDA for the active immunization of pregnant persons between 32 through 36 weeks’ gestation for the prevention of RSV LRTD in infants from birth through 6 months of age.15 Administration of the RSVpreF vaccine to pregnant people elicits the formation of antiRSV antibodies that are transferred transplacentally to the fetus, resulting in the protection of the infant from RSV during the first 6 months of life. The RSVpreF vaccine also is approved to prevent RSV LRTD in people aged ≥ 60 years.
The RSVpreF vaccine contains the prefusion form of the RSV fusion (F) protein responsible for viral entry into host cells. The vaccine contains 60 µg of both RSV preF A and preF B recombinant proteins. The vaccine is administered as a single intramuscular dose in a volume of 0.5 mL. The vaccine is provided in a vial in a lyophilized form and must be reconstituted prior to administration. The average wholesale price of RSVPreF vaccine is $354.16 The vaccine is contraindicated for people who have had an allergic reaction to any component of the vaccine. The most commonly reported adverse reaction is injection site pain (41%).15 The FDA reports a “numerical imbalance in preterm births in Abrysvo recipients compared to placebo recipients” (5.7% vs 4.7%), and “available data are insufficient to establish or exclude a causal relationship between preterm birth and Abrysvo.”15 In rabbits there is no evidence of developmental toxicity and congenital anomalies associated with the RSVpreF vaccine. In human studies, no differences in the rate of congenital anomalies or fetal deaths were noted between RSVpreF vaccine and placebo.
In a clinical trial, 6,975 pregnant participants 24 through 36 weeks’ gestation were randomly assigned to receive a placebo or the RSVpreF vaccine.15,17 After birth, follow-up of infants at 180 days, showed that the rates of MA RSV LRTD among the infants in the placebo and RSVpreF vaccine groups were 3.4% and 1.6%, respectively. At 180 days, the reported rates of severe RSV LRTD in the placebo and RSVpreF vaccine groups were 1.8% and 0.5%, respectively. In this study, among the subset of pregnant participants who received the RSVpreF vaccine (n = 1,572) or placebo (n = 1,539) at 32 through 36 weeks’ gestation, the rates of MA RSV LRTD among the infants in the placebo and RSVpreF vaccine groups were 3.6% and 1.5%, respectively. In the subset of pregnant participants vaccinated at 32 through 36 weeks’ gestation, at 180 days postvaccination, the reported rates of severe RSV LRTD in the placebo and RSVpreF vaccine groups were 1.6% and 0.4%, respectively.15
The CDC has recommended that the RSVpreF vaccine be administered to pregnant people 32 through 36 weeks’ gestation from September through the end of January in most of the continental United States to reduce the rate of RSV LRTD in infants.6 September was selected because it is 1 to 2 months before the start of the RSV season, and it takes at least 14 days for maternal vaccination to result in transplacental transfer of protective antibodies to the fetus. January was selected because it is 2 to 3 months before the anticipated end of the RSV season.6 The CDC also noted that, for regions with a different pattern of RSV seasonality, clinicians should follow the guidance of local public health officials. This applies to the states of Alaska, southern Florida, Hawaii, and Puerto Rico.6 The CDC recommended that infants born < 34 weeks’ gestation should receive nirsevimab.6
Maternal RSV vaccination is thought to be cost-effective for reducing RSV LRTD in infants. However, the cost-effectiveness analyses are sensitive to the pricing of the two main options: maternal RSV vaccination and nirsevimab.
It is estimated that nirsevimab may provide greater protection than maternal RSV vaccination from RSV LRTD, but the maternal RSVpreF vaccine is priced lower than nirsevimab.18 Focusing administration of RSVpreF vaccine from September through January of the RSV infection season is thought to maximize benefits to infants and reduce total cost of the vaccination program.19 With year-round RSVpreF vaccine dosing, the estimated ICER per quality-adjusted life-year (QALY) is approximately $400,000, whereas seasonal dosing reduces the cost to approximately $170,000.19
RSV prevention strategy 3
Vaccinate pregnant persons; reflex to newborn treatment with nirsevimab if maternal RSV vaccination did not occur
RSVpreF vaccination to all pregnant persons 32 through 36 weeks’ gestation during RSV infection season is not likely to result in 100% adherence. For instance, in a CDC-conducted survey only 47% of pregnant persons received an influenza vaccine.2 Newborns whose mothers did not receive an RSVpreF vaccine will need to be considered for treatment with nirsevimab. Collaboration and communication among obstetricians and pediatricians will be needed to avoid miscommunication and missed opportunities to treat newborns during the birth hospitalization. Enhancements in electronic health records, linking the mother’s vaccination record with the newborn’s medical record plus an added feature of electronic alerts when the mother did not receive an appropriately timed RSVpreF vaccine would improve the communication of important clinical information to the pediatrician.
Next steps for the upcoming peak RSV season
We are currently in the 2023–2024 RSV infection season and can expect a peak in cases of RSV between December 2023 and February 2024. The CDC recommends protecting all infants against RSV-associated LRTD. The options are to administer the maternal RSVpreF vaccine to pregnant persons or treating the infant with nirsevimab. The vaccine is just now becoming available for administration in regional pharmacies, physician practices, and health systems. Obstetrician-gynecologists should follow the recommendation of their state department of public health. As noted above, many state departments of public health are recommending that all newborns receive nirsevimab. For clinicians in those states, RSVPreF vaccination of pregnant persons is not a priority. ●