Use of the Pfizer Respiratory Syncytial Virus Vaccine …

Recommendations for Use of RSVpreF Vaccine in Pregnant Persons

On September 22, 2023, ACIP and CDC recommended maternal Pfizer RSVpreF vaccination in pregnant persons as a one-time dose at 32 weeks and zero days’–36 weeks and 6 days’ gestation using seasonal administration (meaning September–January in most of the continental United States) for prevention of RSV-associated LRTI in infants aged <6 months.**** These recommendations will be updated as new evidence becomes available.

Clinical Guidance

Seasonal Administration of RSVpreF Vaccine. Maternal RSVpreF vaccine should be administered to pregnant persons during September–January in most of the continental United States to target vaccine to pregnant persons whose infants will be in their first months of life, when protection from maternal vaccination would be at its highest, during the RSV season. Administering maternal RSVpreF vaccine starting in September (1–2 months before the anticipated start of the RSV season) and continuing through January (2–3 months before the anticipated end of the RSV season) will maximize cost-effectiveness and benefits. In jurisdictions with RSV seasonality that differs from most of the continental United States, including Alaska, southern Florida, Guam, Hawaii, Puerto Rico, U.S.-affiliated Pacific Islands, and U.S. Virgin Islands, providers should follow state, local, or territorial guidance on timing of maternal RSVpreF vaccination.^††††

Simultaneous Administration with Other Vaccines. In accordance with CDC’s General Best Practices Guidelines for Immunization, maternal RSVpreF vaccine can be administered to pregnant persons with other recommended vaccines, such as tetanus, diphtheria, and pertussis (Tdap), influenza, and COVID-19 vaccines, without regard to timing, including simultaneous vaccination at different anatomic sites on the same day (18).

Additional Vaccine Doses in Subsequent Pregnancies. Currently, no data are available on either the efficacy of the first lifetime dose to protect infants born after subsequent pregnancies or the safety of additional doses given during subsequent pregnancies. Additional data are needed to determine whether additional seasonal doses during subsequent pregnancies are indicated, and ACIP might update recommendations in the future, as data become available.

Updated Clinical Guidance for Use of Nirsevimab and Maternal RSVpreF Vaccine

Recommendations for nirsevimab, a long-acting monoclonal antibody product, have been previously published (3). Either maternal RSVpreF vaccination during pregnancy at 32–36 weeks’ gestation or nirsevimab immunization for infants aged <8 months who are born during or are entering their first RSV season is recommended to prevent RSV-associated LRTI in infants, but administration of both products is not needed for most infants. Providers who care for pregnant persons should discuss the relative advantages and disadvantages of both maternal RSVpreF vaccination and nirsevimab and consider patient preferences when determining whether to vaccinate the pregnant person or to rely on administration of nirsevimab to the infant (Box) (19).

No data are available directly comparing the efficacy of nirsevimab and maternal RSVpreF vaccine in preventing RSV-associated LRTI in infants. Protection conferred through maternal vaccination will likely wane after 3 months, as has been observed in infants born to pregnant persons who have received influenza and COVID-19 vaccines (16,20,21). However, because maternal RSV vaccination at 32–36 weeks’ gestation is recommended during only September–January in most of the continental United States, most infants of vaccinated mothers will be born during an RSV season. Mothers of most infants born outside of RSV season (i.e., during April–September) will not have been vaccinated; therefore, nirsevimab is recommended for these infants at the onset of the RSV season if they are aged <8 months.

At least 14 days are likely needed after maternal vaccination for development and transplacental transfer of maternal antibodies to protect the infant (16,22); therefore, nirsevimab is recommended for infants born <14 days after maternal RSVpreF vaccination. The earliest an infant could be born and be considered protected by maternal receipt of RSVpreF vaccine at 32 weeks’ gestation (the earliest recommended time for vaccination) would be at 34 gestational weeks. Therefore, nirsevimab is recommended for all infants born at <34 weeks’ gestation.

Nirsevimab is recommended for infants aged <8 months born during or entering their first RSV season whose mother did not receive RSVpreF vaccine, whose mother’s receipt of RSVpreF vaccine is unknown, or who were born <14 days after maternal vaccination. Nirsevimab is not needed for most infants aged <8 months whose mother received RSVpreF vaccine ≥14 days before birth. Nirsevimab may be considered for infants born to vaccinated mothers in rare circumstances when, based on the clinical judgment of the health care provider, the potential incremental benefit of administration is warranted. These situations include, but are not limited to, infants born to mothers who might not have mounted an adequate immune response to vaccination (e.g., persons with immunocompromising conditions) or who have conditions associated with reduced transplacental antibody transfer (e.g., persons living with HIV infection) (23); infants who might have experienced loss of maternal antibodies, such as those who have undergone cardiopulmonary bypass (24) or extracorporeal membrane oxygenation; and infants with substantially increased risk for severe RSV disease (e.g., hemodynamically significant congenital heart disease, or intensive care admission requiring oxygen at hospital discharge).

Infants and children aged 8–19 months who are at increased risk for severe RSV disease and are entering their second RSV season are recommended to receive nirsevimab regardless of maternal RSVpreF vaccination (3). Recommendations for timing of nirsevimab administration, coadministration of nirsevimab with routine childhood vaccines, reporting of adverse events, and recommendations for use for infants and children aged 8–19 months who are at increased risk for severe RSV disease and who are entering their second RSV season have been previously published and remain unchanged (3).

Precautions and Contraindications

As with all vaccines, RSV vaccination should be delayed for persons experiencing moderate or severe acute illness with or without fever (precaution). RSV vaccines are contraindicated for and should not be administered to persons with a history of severe allergic reaction, such as anaphylaxis, to any component of the vaccine.

Reporting of Vaccine Adverse Events

Adverse events after vaccination should be reported to the Vaccine Adverse Event Reporting System (VAERS). Reporting is encouraged for any clinically significant adverse event even if it is uncertain whether the vaccine caused the event. Information on how to submit a report to VAERS is available at https://vaers.hhs.gov/index.html or by telephone at 1-800-822-7967.

Future Research and Monitoring Priorities

CDC will monitor adverse events, including preterm birth, hypertensive disorders of pregnancy, and inflammatory neurologic events after RSVpreF vaccination in pregnant persons through VAERS and the Vaccine Safety Datalink (https://www.cdc.gov/vaccinesafety/ensuringsafety/monitoring/vsd/index.html). Reactions and health impacts after RSVpreF vaccination will also be monitored through v-safe. According to FDA post-marketing requirements, the manufacturer will conduct post-marketing studies to assess preterm birth and hypertensive disorders of pregnancy, including preeclampsia (25).