RSV Immunization Administration Frequently Asked Questions

About RSV Immunization

Are nirsevimab and clesrovimab vaccines?

Nirsevimab and clesrovimab are monoclonal antibody products that are passive immunizations. While not technically “vaccines” in a traditional sense (active immunization), they are being used in a manner similar to routine childhood vaccines and may be referred to as vaccines by some entities. 

Nirsevimab and clesrovimab confer long-lasting protection from RSV, with protection expected to last at least 5 months (about the length of a typical RSV season). Nirsevimab and clesrovimab are part of the Vaccines for Children program.

How effective is RSV immunization and how long does the RSV protection conferred by nirsevimab and clesrovimab last?

Protection from RSV immunization is expected to last at least 5 months, about the length of an RSV season, and is expected to reduce the risk of severe RSV disease by about 80%. Data from recent RSV seasons show that nirsevimab is effective in reducing RSV-associated emergency department encounters and hospitalizations among infants in their first RSV season. Findings from multisite electronic health record networks have demonstrated meaningful reductions in RSV-associated emergency department encounters and hospitalizations following nirsevimab administration. 

RSV Immunization Ordering and Supply

Given nirsevimab has a shelf life of about 36 months and clesrovimab has a shelf life of about 30 months, should I purchase extra doses to have on hand knowing I can always use them next season?

Since formulations for RSV mAb products will not change year to year, leftover doses from one season can be kept refrigerated and used in the next season. However, it is also important to consider the cost of the products and potential for vaccine loss due to temperature excursions associated with natural disasters, equipment failure, etc. Choices about quantities of product to purchase are individual, by practice or institution.

How long can nirsevimab and clesrovimab be left at room temperature before discarding?

Nirsevimab can be kept at room temperature (20˚C – 25˚C) for 48 hours, if protected from light. After removal from the refrigerator, nirsevimab must be used within 48 hours or discarded. The 48 hour maximum time out of the refrigerator can be continuous or cumulative. Use Sanofi’s Stability Calculator to determine whether nirsevimab can be used based on cumulative time out of the refrigerator.

Clesrovimab may be kept at room temperature between 68°F to 77°F (20°C to 25°C) for a maximum of 48 hours. After removal from the refrigerator, clesrovimab must be used within 48 hours or discarded. The 48 hour maximum time out of the refrigerator can be continuous or cumulative.

Nirsevimab-Specific Questions

Can I administer two 50 mg doses of nirsevimab to my patient who is > 5 kg instead of a 100 mg dose?

Avoid using two 50 mg nirsevimab doses for infants weighing ≥5 kilograms (≥11 pounds), because 50 mg doses should be reserved for smaller infants who are at increased risk for severe RSV illness. Furthermore, providers should be aware that insurers may not cover the cost of two 50 mg nirsevimab doses for an individual patient.

Can we split a 100 mg manufacturer-filled syringe (MFS) of nirsevimab into two 50 mg doses?

No, nirsevimab 100 mg doses are approved for single use.  They are intended for ONE patient for ONE injection. Never administer medications from the same syringe to more than one patient, even if the needle is changed.  
 
Manufacturer-filled syringes are prepared with a single dose and sealed under sterile conditions by the manufactures. They do not contain a preservative to help prevent the growth of microorganisms.  Attempting to split 100 mg MFS into two 50 mg doses is a serious administration error that risks inadvertent contamination and infection transmission.

RSV Immunization Administration, Side Effects/Contraindications, and Timing

Because nirsevimab and clesrovimab are monoclonal antibody products, who can administer them?

Nirsevimab and clesrovimab come in prefilled syringes. In most states, anyone who can administer injections can administer nirsevimab and clesrovimab.

Can RSV immunization be co-administered with other routine vaccines?

Yes. In accordance with Immunize.org and AAP policy guidance, simultaneous administration of RSV immunization with age-appropriate vaccines is recommended. Nirsevimab and clesrovimab are not expected to interfere with the immune response to other vaccines and had similar safety and reactogenicity profiles to vaccines administered without nirsevimab or clesrovimab.

Are there maximum volumes of injectable vaccine, antibiotic or other products that can be administered into each muscle group for different ages? For example, at the 6-month well-child visit, could an infant receive RSV immunization, COVID-19, influenza, PCV, and DTaP-IPV-HepB-Hib?

In accordance with Red Book guidance, simultaneous administration of RSV immunization with age-appropriate vaccines is recommended.  

The volumes that can be injected into each muscle group differ by age. In the deltoid region, the range is 0.5-2 mL, while in the vastus lateralis region the range is 1-5 mL. Healthcare providers should always use professional judgement when administering injections, as muscle size can vary greatly from one patient to another.

Strategies healthcare providers can use to decrease the number/injection volume include:

1. Include an age-appropriate combination vaccine in the facility’s inventory (eg, Pentacel, Pediarix, Vaxelis, ProQuad).
2. Use an alternate route (other than IM) if possible. IPV (single component, NOT a combination vaccine), MMR (toddlers and infant travelers only), Varicella-containing vaccines (toddlers only), and PPSV23 (high-risk toddlers only) can be administered subcutaneously.
3. Take advantage of recommended age ranges some of the routinely recommended vaccines have. For example, the 3rd dose of HepB can be given as late as 18 months of age to children born to mothers who are HBsAg negative.

The current recommendation is that if an infant’s pregnant parent received RSV vaccine < 14 days prior to the infant’s birth, the infant should receive RSV immunization. In this scenario, is there a minimum interval between RSV vaccine (Abrysvo) administration in the pregnant parent and administration of RSV immunization (ie. nirsevimab or clesrovimab) in the infant?

No, there is no minimum interval.

What does "shortly before or during” the RSV season mean? When should I start and stop administering RSV immunizations?

RSV immunization should be administered during October through the end of March in most of the continental United States. However, recommendations on the timing of RSV immunization are intentionally flexible to optimize patient access, including insurance payment. For example, in Alaska RSV circulation patterns are less predictable, and the duration of the RSV season is often longer than the national average. Tropical climates might also have RSV circulation patterns that differ from most of the continental US or are unpredictable. In addition, because the timing of RSV activity varies geographically in other regions of the US, public health authorities may elect to provide revised guidance regarding the timing of RSV immunization administration based on local surveillance data and feasibility of implementation (ie, extending or shortening the recommended administration period of October–March). Public health authorities should consider the advantages and disadvantages of modifying the timing of administration. Providers, including regional medical centers and health systems, should consult with state or territorial health departments before systematically modifying the recommended months for RSV immunization administration for their eligible patient populations. For more information, including an outline of potential advantages and disadvantages of modifying timing of administration, see http://dx.doi.org/10.15585/mmwr.mm7432a3.

Under special circumstances (eg, travel to areas of increased RSV activity, concern of failure to return for administration), health care providers may use clinical judgment in determining when to administer RSV antibody outside the months of October through March to individual patients.  For example, healthcare providers may choose to give nirsevimab or clesrovimab shortly before the start of RSV season (eg., September) if they feel that the eligible child may not return for a visit when RSV immunization would be recommended. Nirsevimab and clesrovimab have been shown to protect against severe RSV disease for at least 5 months, and the ideal timing of administration may differ depending on the clinical situation.

If a high-risk child mistakenly received a 100 mg dose of nirsevimab when they should have received a 200 mg dose, should we have them return for the other 100mg?

If a half dose is inadvertently given, another half dose should be administered as soon as possible, but no later than the end of the season (for most of the continental US, this would be through the end of March, unless local public health authorities recommend administering during a modified time period). This counts as a 200 mg dose.

What are the potential side effects of RSV immunization?

The AAP provides Immunization Facts for Families, one-page handouts that can be provided to families during immunization conversations or after immunization administration. Fact Sheets include family-friendly language about potential side effects.

Immunize.org published an Immunization Information Statement (VIS-like document) for families. It states that “After getting an RSV preventive antibody, your child might have temporary pain, redness, swelling where the injection was given, or a rash.”  In addition, the nirsevimab package insert and clesrovimab package insert have additional information on adverse reactions. For nirsevimab, “Most common adverse reactions were rash (0.9%) and injection site reactions (0.3%).” For clesrovimab, “Most common adverse reactions were injection-site erythema (3.8%), injection site swelling (2.7%), and rash (2.3%).

Are there any contraindications to receiving RSV immunization? Can an infant or young child receive RSV immunization when they are sick?

Both nirsevimab and clesrovimab are contraindicated in infants and young children with a history of serious hypersensitivity reactions, including anaphylaxis, to nirsevimab or clesrovimab or to any of their components. Illness or febrile diseases are not contraindications to receiving an RSV immunization. The AAP suggests following Immunize.org guidance, which recommends that vaccination should be deferred for persons with a moderate or severe acute illness, as this precaution avoids causing diagnostic confusion between the underlying illness and potential adverse effects of immunization. Similar to routine childhood vaccines, mild illness – with or without fever – should not be used as a reason to delay administration of nirsevimab or clesrovimab.  

RSV Vaccine for Adolescents

What was the scope of AAP’s focus on RSV prevention?

AAP's clinical questions, and corresponding evidence review of RSV disease prevention, focused primarily on monoclonal antibody products (nirsevimab and clesrovimab), for which high-quality pediatric evidence and surveillance data are available

Does AAP recommend RSV vaccination for adolescents?

The RSV vaccine is distinct from the monoclonal antibody products, clesrovimab and nirsevimab. For the 2026–2027 season, AAP did not make specific recommendations on RSV vaccination for pediatric populations, including for immunocompromised adolescents. RSV vaccines are not licensed for this age group, and pediatric data on safety, dosing, immunogenicity, and effectiveness remain limited.

Will AAP make recommendations for RSV vaccine in the future?

When high-quality evidence on RSV vaccination in younger age groups becomes available, AAP may include it in future evidence reviews and recommendations. The current available evidence for the three RSV vaccines licensed in the United States include small sample size studies in two Phase 1 trials for Abrysvo and mResvia and there have been no reported results for Arexvy. For more information, see https://www.ema.europa.eu/en/documents/variation-report/abrysvo-h-c-006027-p46-006-epar-assessment-report_en.pdf.

Why are there differences in guidance issued by professional societies?

For the 2026–2027 respiratory virus season, professional societies addressed different populations in their recommendations for RSV prevention. For example, the guidance from the American College of Obstetricians and Gynecologists (ACOG) focused on the RSV vaccine in pregnancy. AAP focused on broad populations of infants and children.  The Infectious Diseases Society of America (IDSA) focused on immunocompromised populations. IDSA separately advised that clinicians may consider off-label RSV vaccination for immunocompromised adolescents on an individual basis after discussions with patients and families, given the limited evidence.

RSV Immunization Recommendations

What are the AAP recommendations for RSV immunization?

The AAP recommends RSV immunization with nirsevimab or clesrovimab shortly before or during RSV season for:

• infants <8 months of age born during or entering their first RSV season if:
  
  • pregnant parent did not receive RSVpreF vaccine during this pregnancy,
  • pregnant parent’s RSVpreF vaccination status is unknown, or
  • infant was born <14 days after the pregnant parent’s RSVpreF vaccination

The AAP recommends RSV immunization with nirsevimab only shortly before or during RSV season for:

• Infants and children 8–19 months of age at high risk of severe RSV disease and entering their second RSV season, regardless of the RSV vaccination status of the pregnant parent or the child’s prior receipt of nirsevimab or clesrovimab when <8 months of age in their first RSV season: administer 1 dose nirsevimab shortly before start of second RSV season. High-risk criteria include the following:
  
  • Children born preterm, at <32 weeks, 0 days’ gestation, regardless of the need for medication or other support
  • Children with chronic lung disease attributable to prematurity or to other significant neonatal conditions (eg, meconium aspiration or congenital diaphragmatic hernia) who required medical support (ie, chronic corticosteroid therapy, diuretic therapy, or supplemental oxygen) at any time during the 6-month period before the start of the second RSV season
  • Children with hemodynamically significant congenital heart disease (ie, a defect that can result in symptoms and/ or cardiac chamber dilation)
  • Children with anatomic pulmonary abnormalities or neuromuscular disorders that put them at risk for severe RSV disease
  • Children with severe immunocompromise
  • Children with Down syndrome or other chromosomal differences placing them at higher risk of severe RSV disease
  • Children with cystic fibrosis who have either manifestations of severe lung disease (previous hospitalization for pulmonary exacerbation in the first year after birth or abnormalities on chest imaging that persist when stable) or weight-for-length that is less than the 10th percentile
  • American Indian or Alaska Native children. American Indian or Alaska Native children are included in the high risk category because they experience significantly higher rates of severe RSV disease and hospitalization associated with social drivers of health, with children living in rural and reservation communities most impacted.

Note that all ages refer to chronologic age, not corrected age.

Should I administer RSV immunization to an infant who is born at the very end of the RSV season?

Yes. Optimal timing for administration is within 1 week after birth during the RSV season. Administering RSV immunization through the end of the season (either March 31 or as determined by a state public health authority) is important because the risk of severe disease is highest during the first few months of life. Even when the season is over, RSV infections still occur, but at a lower incident rate. 

If an infant’s gestational parent received RSV vaccine while pregnant with the infant, should the infant receive nirsevimab or clesrovimab?

The AAP does not recommend RSV immunization for most infants born to a mother who received maternal RSV vaccine during their most recent pregnancy. The exception is infants where less than 14 days have elapsed between vaccination and birth. In this situation, the infant should receive nirsevimab or clesrovimab per AAP recommendations.   

RSV immunization can also be considered for infants born to a mother who received maternal RSV vaccine when, per the clinical judgement of the healthcare provider, the potential incremental benefit of administration is warranted, including but not limited to the following rare circumstances:

• Infants whose birthing parent may not have mounted an adequate immune response to RSV vaccination (eg, pregnant people with immunocompromising conditions)
• Infants whose birthing parent has a medical condition associated with reduced transplacental antibody transfer (eg, pregnant people living with HIV infection)
• Infants who have undergone antibody-depleting treatments or procedures such as plasmapheresis, cardiopulmonary bypass (see FDA package inserts at www.fda.gov/drugsatfda), or ECMO or exchange transfusion, leading to loss of maternal antibodies
• Infants with substantial increased risk for severe RSV disease (eg, hemodynamically significant congenital heart disease, intensive care admission with a requirement of oxygen at discharge)

I have a healthy patient who was 7 months old in October. They present to the clinic in November, at 8 months of age. Can they receive RSV immunization at this visit?

No. AAP recommends that only those healthy infants younger than 8 months of age at the time of administration receive RSV immunization.

Can a baby who is 9 months old but corrects to 7 months due to prematurity (delivery at 33 weeks gestational age) receive RSV immunization?

If the infant does not meet second season criteria, they would not be eligible for RSV immunization. In accordance with CDC General Best Practice Guidelines for Immunization preterm infants (infants born before 37 weeks’ gestation), regardless of birth weight, should receive RSV immunization at their chronological age using the same guidance for full-term infants and young children.  

Will infants born during the RSV season receive RSV immunization before they are discharged from the hospital?

It is recommended that infants born shortly before and during the RSV season receive RSV immunization within the first week of life, including in hospital settings. If a hospital has been unable to implement administration of RSV immunizations, the infant should receive it in an ambulatory setting as soon as possible. Not all birthing hospitals are administering RSV immunization to all newborns, and additional advocacy is ongoing. Timely and well-coordinated communication between birth hospital and the medical home is important. Equitable access to RSV immunization will require those in a community to work together.

Infants with prolonged birth hospitalizations because of prematurity or other causes should receive RSV immunization shortly before or promptly after discharge. Health care–associated RSV disease occurs; however, the incidence is unknown. Safety data for use of RSV immunization in infants with a postmenstrual age (gestational age at birth plus chronologic age) of <32 weeks are limited. To prevent health care-associated RSV disease, providers may consider administering RSV immunization to eligible hospitalized infants during their hospitalization. This decision should be based on clinical judgment, considering the potential risks and benefits as well as local RSV activity. For more information, see https://www.cdc.gov/mmwr/volumes/74/wr/mm7432a3.htm

If a patient was born towards the end of March or in April and did NOT receive RSV immunization shortly after birth, can they receive RSV immunization if they are < 8 months of age entering their second RSV season? If our facility is administering nirsevimab, should this infant receive a 100 mg or 200 mg dose?

Yes. Per AAP’s guidance, healthy infants born at the end of their first RSV season who did NOT receive RSV immunization (and whose birthing parent did not receive RSV vaccine during pregnancy) may receive one dose of RSV immunization if they are < 8 months of age entering their second RSV season.

An infant’s first dose of RSV immunization, administered at < 8 months of age, should be consistent with first season dosing (ie. 100 mg nirsevimab or 105 mg clesrovimab). 

Should a standard risk patient born in March or April (during an extended RSV season) who received a dose of RSV immunization shortly after birth, receive another dose of RSV immunization if they are < 8 months of age entering their second RSV season?

No. The infant is not eligible to receive RSV immunization since they received a dose during their first RSV season. Only children who meet high-risk criteria should receive more than one dose of RSV immunization. For more details on high-risk criteria, please see the full AAP recommendations here.

Why are infants 8-12 months old ineligible to receive RSV immunization (unless they are considered high-risk)?

The highest risk for severe RSV is in children under 6 months of age. Infants 8 months and older will be entering their second RSV season and have likely already experienced their first RSV infection and will not receive the full benefits of RSV immunization.  

What is the guidance for high risk infants who are 19-24 months of age, particularly given nirsevimab has been FDA approved for infants and toddlers 24 months of age and younger who are at high risk for severe RSV illness?

A dose of nirsevimab is recommended for some children aged 8 through 19 months who are at increased risk for severe RSV and who are entering their second RSV season (note this is inclusive of 19 months). Nirsevimab provides at least 5 months of protection and should be offered to eligible children when entering the RSV season.

Nirsevimab is not recommended for any child who is age 20 months and older. Children ages 20 months and older have likely already experienced two RSV seasons and been infected with RSV, and thus are less likely to benefit from nirsevimab. Clesrovimab is not recommended for any child who is age 8 months and older.

Should an infant who had a confirmed RSV infection this season still receive RSV immunization?

Prior infection should generally not be used to determine an infant’s eligibility for RSV immunization.

What if a young infant is in our office and diagnosed with RSV that day or are within 48 hours of illness onset? Would a dose of RSV immunization be helpful to them to reduce the severity of the illness?

Nirsevimab and clesrovimab have not been studied as a treatment in infants with RSV and is not licensed for treatment of RSV disease. RSV immunization should be given prior to onset of the RSV season or as soon as possible after birth for infants born during the season to prevent severe RSV disease.

Coding, Payment, and Reporting

How do I code and bill for RSV immunization? Will I be paid appropriately?

See current coding and billing recommendations, including Coding Vignettes, on the Coding & Payment For RSV Immunizations page.

Does RSV immunization require insurance prior authorization?  

In most instances, RSV immunization does not require insurance preauthorization. Please report any payer concerns or hassles to the Coding & Payment Hotline.

If a patient has an adverse reaction to RSV immunization, where should it be reported?

Adverse events when giving an RSV immunization alone should be reported to the FDA’s MedWatch Adverse Event Reporting Program.  

If an adverse event occurs while co-administering RSV immunization with a vaccine, it should be reported to the Vaccine Adverse Event Reporting System.