RSV Frequently Asked Questions (FAQs)

This webpage is designed to help providers and local health department staff stay abreast on the latest information on RSV immunizations.

What is RSV?
Respiratory syncytial virus, or RSV, is a common respiratory virus that usually causes colds, but may cause severe disease in infants and older adults. In the United States, RSV usually starts in the fall season and peaks in the winter.

RSV is the leading cause of hospitalization and the most common cause of bronchiolitis and pneumonia in children younger than 1 year of age in the United States. Almost all children get RSV at least once before they are two years of age. 

In adults, the risk of severe RSV illness also increases with age. Infections are especially dangerous for older adults or those with underlying medical conditions. Each year an estimated 60,000-160,000 older adults are hospitalized and up to 10,000 die due to RSV.
 

Jump to RSV immunization information for:

• Infants
• Pregnant People 
• Adults

Beyfortus (nirsevimab) and Enflonsia (clesrovimab): RSV Immunization (Monoclonal Antibody) for Infants
 

1. What are the recommendations for infant and toddler RSV immunizations?                          
   RSV immunizations are recommended for all infants 0-8 months of age who are born during or entering their first RSV season (generally October – March) if the parent’s prenatal RSV vaccination status is: unvaccinated, unknown or vaccinated < 14 days before birth. Infants born during the RSV season should receive a dose within 1 week of birth, ideally in birth hospitalization. These infants may receive either: 

• nirsevimab: 50mg for infants <5kg or 100mg for infants > 5kg
  OR
• clesrovimab: 105mg regardless of weight

​Infants younger than 8 months of age born in the months outside of the RSV season should get imunized in October or November. Infants and toddlers 8-19 months at increased risk of severe RSV disease and entering their second RSV season should receive a 200mg dose of nirsevimab. Please note: For the 2025-26 RSV season, IHS guidance is the preferential use of nirsevimab for Ai/AN eligible infants and children.

For additional details on RSV immunizations, please refer to the RSV Immunization Guide to Prevent Severe RSV in Infants and Toddlers.

2. How long do RSV immunizations provide protection?             
   Protection is expected to last for at least 5 months (the length of an average RSV season).

3. How effective is Beyfortus (nirsevimab) immunization in infants?
   An early estimate based on data collected between October 2023 – February 2024 from infants <8 months of age suggests that nirsevimab is 90% effective in keeping immunized infants from being hospitalized with RSV-associated infection in the first months after administration. 
    
4. If a patient <5kg comes to an ambulatory clinic and only the 100mg dose version of nirsevimab is available, can half the syringe be given to this patient?
   No. Nirsevimab is supplied as a prefilled syringe in 50 or 100mg doses. For children weighing <5kg, an appropriate 50mg dose using the 50mg prefilled syringe should be used for this patient, as per the manufacturer’s instructions in the package insert: label (fda.gov). Splitting prefilled syringes into multiple doses could lead to potential risk of dosing errors, dose wastage, or contamination of the prefilled syringe, and thus should not be done.
    
5. May I administer two 50mg instead of the 100mg dose of nirsevimab if the 100mg dose is not available or if I need to use up inventory?
   No. You should not administer two 50mg doses instead of a 100mg dose of nirsevimab under any circumstance for three main reasons:

• Sufficient supply. There is currently sufficient supply of both the 50mg and 100mg syringes. Providers should administer the indicated syringe for their patients and place additional orders, as needed.
• Long shelf life. Nirsevimab has an 18-month shelf life and can often be stored for future use if not near expiration. You may consider labeling these doses: “Keep for Fall.” If doses are near expiration, contact your field representative for potential transfer options.
• Cost: Administering two 50mg doses is more expensive ($1112) compared to a single 100mg dose ($556), and some insurance plans may not cover two 50mg doses for one infant.

6. Can you administer RSV immunizations with other vaccines recommended for infants and young children?
   Yes! It is safe to administer the RSV immunization at the same time as other recommended immunizations for children, including influenza and updated COVID-19 vaccines.
    
7. Will private insurance cover RSV immunizations for infants?
   The Affordable Care Act (ACA) typically requires coverage for all immunizations administered in accordance with ACIP recommendations. Individuals, or their healthcare providers, should contact their health insurance plan to see if and when RSV immunizations are covered along with reimbursement requirements.
    
8. Are RSV immunizations available through the Vaccines for Children (VFC) Program? 
   Yes. Beyfortus (nirsevimab) is now available through the VFC Program. Since clesrovimab (Enflonsia) was recently approved by FDA and recommended by ACIP in June 2025, the timeline for availability of this new product is not yet known. Once celsrovimab is available from VFC, we will send a clinical letter detailing more information about the new product and ordering.
    
9. Are VFC providers required to offer RSV immunizations?
   Yes. VFC providers are required to offer nirsevimab or clesrovimab if they see patients in that age group, along with all other age-appropriate ACIP-recommended vaccines. See VFC’s provider requirements for more detail. 

10. Which staff members may administer RSV immunizations? 
    Staff members that may administer nirsevimab include physicians, physician assistants, nurses, medical assistants, pharmacists and pharmacy interns, assuming that they meet their usual conditions for immunizing. 
    ​​​
11. ​​Am I able to record doses of Beyfortus (nirsevimab) and Enflonsia (clesrovimab) for infants in CAIR now? ​                    Yes! Beyfortus (nirsevimab) is in CAIR under the brand name “Beyfortus” and Enflonsia (clesrovimab) is in CAIR now under the brand name “Enflonsia.”
    ​
12. Am I required to record RSV immunization doses for infants in CAIR?                                                                                    Yes, it is a requirement. Per California law, please ensure all immunizations administered are entered into a California Immunization Registry (CAIR or RIDE).
     
13. Where should I report adverse events following RSV immunization administration?​​​ ​​
    If nirseviman or clesrovimab is administered alone, report side effects to the MedWatch website online, by fax, by mail, or by calling 1-800-FDA-1088. If nirsevimab or clesrovimab is administered with any vaccine on the same day, report side effects to the Vaccine Adverse Event Reporting System (VAERS). Reports should specify that the patient received nirsevimab or clesrovimab on the VAERS form in Section 9: “Prescriptions, over-the-counter medications, dietary supplements, or herbal remedies being taken at the time of vaccination.” Reports can be submitted to VAERS online, by fax, or by mail. Additional information about VAERS is available by telephone (1-800-822- 7967) or online. When adverse reactions that occur after the coadministration of infant RSV antibodies with a vaccine are reported to VAERS, additional reporting of the same adverse reactions to MedWatch is not necessary.

14. Is there a list of birthing hospitals that are currently offering RSV immunization to newborns? ​
    Yes! CDPH recognizes birthing hospitals enrolled in VFC and administering RSV immunizations to VFC-eligible newborns. If your birthing hospital is not listed, please ask their leadership to reach out to the VFC Team at VFCEnrollment@cdph.ca.gov for enrollment assistance.

RSV Vaccine for Pregnant People
 

1. What is the RSV vaccine recommendation for pregnant people?
   CDC recommends RSV vaccine, Abrysvo, for all pregnant people at 32 through 36 weeks gestation, using seasonal administration (September—January), to prevent RSV-associated lower respiratory tract infection in infants. Abrysvo is the only RSV vaccine approved for pregnant persons. Arexvy and mRESVIA are NOT approved for pregnant persons.                                                                                                                                                                       
2. When is prenatal immunization against RSV recommended to be given?
   CDC recommends that immunization against RSV (with Abrysvo) be administered to all pregnant persons at 32-36 weeks gestation from September through the end of January. For people who previously received the maternal RSV vaccine (Abrysvo), during future pregnancies they are NOT recommended to receive additional vaccine doses and their infants should receive nirsevimab.

   As an alternative, administration to infants after birth of the remaining doses of nirsevimab is recommended by CDC in most of the US through the end of March – Please continue to administer your remaining doses of nirsevimab to protect infants and toddlers against RSV if prenatal immunization was not given.             
                                                                                                                
   Please note that: Both RSV vaccine and nirsevimab have a lengthy shelf life and are expensive. Save unused doses for the following RSV season and consider labeling as “Keep for Fall.” Unused and unexpired doses of VFC RSV vaccines cannot be returned to McKesson. Privately purchased doses of ABRYSVO may continue to be used year-round to protect patients 60 years and older (while VFC supplies are indicated for pregnant adolescents).  

3. Are infants recommended to receive Beyfortus (nirsevimab) if their birthing parent was immunized during pregnancy?  Most infants will likely only need protection from either the prenatal RSV vaccine or infant immunization, but not both. Infants <8 months entering their first RSV season should receive RSV immunization if their birth parent’s prenatal RSV vaccination status is: unvaccinated, unknown or vaccinated <14 days before birth. In some limited cases, an infant may be eligible to receive both immunizations.                                                                                            

4. How long does protection from prenatal RSV vaccine last?
   In the clinical trials for the RSV vaccine given during pregnancy, infants through 6 months of age were protected against RSV-associated lower respiratory tract infection. The clinical trials did not measure protection beyond 6 months of age.
    
5. Can prenatal RSV vaccine be co-administered with other prenatal vaccines such as Tdap, flu and COVID-19 vaccines?
   Yes. You can receive the RSV vaccine on the same day as other vaccines recommended during pregnancy, including Tdap, COVID-19, and influenza.
    

6. What is safety profile of prenatal RSV vaccine?
   In the clinical trials, the side effects most often reported by pregnant people who received prenatal RSV vaccine were pain at the injection site, headache, muscle pain, and nausea.The clinical trials identified a small increase in the numbers of vaccinated pregnant people with preterm births or very high blood pressure. It is not clear if this was a chance finding or somehow related to RSV vaccine. To mitigate this theoretical risk, prenatal RSV vaccine is indicated in the late trimester at 32 to 26 weeks gestation. CDC and FDA are continuing to monitor the safety of prenatal RSV vaccine. 
    

7. Is the prenatal RSV vaccine covered by Medi-Cal and private insurance?
   The Affordable Care Act (ACA) typically requires coverage for all immunizations administered within the year after the ACIP recommendation. Medi-Cal also offers immunizations as a medical and pharmacy benefit. Prenatal care providers who do not stock prenatal immunizations should provide strong referrals to patients’ in-network pharmacies. Individuals, or their healthcare providers, should contact their health insurance plan to see if and when the immunization is covered along with reimbursement requirements.
    
8. How can a provider evaluating a baby for Beyfortus (nirsevimab) determine if the baby’s birthing parent received prenatal RSV vaccine?
   If prenatal records are unavailable to determine if the baby’s birthing parent was immunized during pregnancy, the birthing parent may request an immunization history report from their prenatal care provider or access their Digital Vaccine Record at MyVaccineRecord.cdph.ca.gov. The immunizing provider may also check the California Immunization Registry (CAIR) to confirm receipt of prenatal RSV vaccine at least 14 days before delivery or postnatal nirsevimab at the birth hospital or clinic.

9. How should prenatal RSV vaccination be documented?
   It is critically important to document receipt of maternal RSV vaccine as most infants of vaccinated mothers are not recommended to receive nirsevimab. Documentation should occur in the:

   • Immunization Information System (CAIR or Healthy Futures)
   • Electronic Health Records (EHRs)
   • Written documentation for patient to bring to birthing hospital and pediatric provider visits.
    

10. Is V-safe available for RSV vaccine given to pregnant people?
    Yes! V-safe is now available for RSV vaccines given to pregnant people. V-safe is a safety monitoring system that lets you share with CDC how they, or their dependent, feels after getting an RSV vaccine. Patients can register at CDC’s V-safe website.
     
11. If a pregnant person received RSV vaccine before 32 weeks of pregnancy, should they get another dose of RSV vaccine between 32 to 36 weeks and should their infant receive nirsevimab?

For doses given before 24 weeks gestation:

• Do not repeat the dose
• For RSV prevention, the infant should receive nirsevimab shortly before or during the first RSV season (at age <8 months).

For doses given during 24 weeks and 0 days’ and 31 weeks and 6 day’s gestation:

• Do not repeat the dose
• All infants born <34 weeks’ gestation should receive nirsevimab.
• Infants born after 34 weeks do not need nirsevimab. This is based on data from the Pfizer phase 3 trial, in which efficacy was assessed among participants who received vaccination during 24 through 36 weeks gestation

RSV Vaccines (Abrysvo, Arexvy, and mRESVIA) for Adults  

1. Who should receive the RSV vaccine for adults?
   Adults 50-74 years who are at increased risk of severe RSV disease and all adults 75 years and older should receive a single dose of RSV vaccine. Persons who have already received RSV vaccination are NOT recommended to receive another dose. RSV vaccines may be administered year-round to adults, CDC encourages providers to maximize benefits of adult RSV vaccination by offering in the late summer or early fall.                                               
                     
2. How many doses of RSV vaccine do I give and how long does RSV vaccine provide protection?                                            One dose of RSV vaccine is recommended at this time. RSV vaccines are highly effective and have been shown to provide protection for at least two RSV seasons. Additional surveillance and evaluation activities are planned to assess whether additional doses will be needed in the future.    
    
3. Can you administer the RSV vaccine with other vaccines recommended for adults?
   Yes! It is safe to administer RSV vaccine with other recommended vaccines, including influenza and COVID-19 vaccines.
    
4. Is RSV vaccine covered by Medicare and private insurance?
   The RSV vaccine is covered by Medicare Part D only (NOT Part B). The Affordable Care Act (ACA) typically requires coverage for all immunizations administered within the year after the ACIP recommendation. Starting January 2023, Part D plans may not apply a deductible or other enrollee cost-sharing requirement for ACIP-recommended vaccines. Individuals, or their healthcare providers, should contact their health insurance plan to see if and when the immunization is covered along with reimbursement requirements.
    
5. Is RSV vaccine available through the Vaccines for Adults (VFA) Program for uninsured or underinsured adults?
   Yes, however available quantities are limited. Please check with VFA for updates. You can contact the VFA program at my317vaccines@cdph.ca.gov.
    
6. Am I able to record doses of RSV vaccines (Abrysvo, Arexvy, amd mRESVIA) in CAIR now?
   Yes! You can record doses administered of Abrysvo, Arexvy or mRESVIA in CAIR.  Doses are valid when administered to persons 50 years of age or older.  Per California law, please ensure all vaccines administered are entered into the Immunization Registry (CAIR or RIDE).
    
7. Is V-safe available for RSV vaccine?
   Yes, v-safe is available for RSV vaccines. V-safe is a safety monitoring system that lets your patients share with CDC how they, or their dependent, feels after getting an RSV vaccine. Patients can register at CDC’s V-safe website.

For additional information, please see RSV Resources.