The Maine Immunization Program (MIP) is now offering Enflonsia (clesrovimab) for the prevention of RSV (respiratory syncytial virus) in neonates and infants who are born during or entering their first RSV season. 

Ordering Options

• 1 – pack (prefilled syringe): Maximum 10 doses per site, per order. 

• 10 – pack (prefilled syringe): Maximum 20 doses per site, per order. 

Orders for Enflonsia must be placed separately from regular vaccine orders in ImmPact. Combined orders will be denied. 

Who should get Enflonsia (clesrovimab)? 

Neonates and infants born during or entering their first RSV season

• Dose: 105 mg (0.7 mL) administered as a single intramuscular (IM) injection

Born during the RSV season

• Administer at birth

Born outside the RSV season

• Administer prior to the start of their first RSV season (considering the duration of protection)

Undergoing cardiac surgery with cardiopulmonary bypass during or entering their first RSV season

• An additional 105 mg IM dose is recommended after surgery once stable, to maintain adequate clesrovimab-cfor serum levels

Storage and Handling

• Store prefilled syringes refrigerated at 36°F to 46°F (2°C to 8°C).   

• Keep prefilled syringes in the original carton, protected from light until use. 

• Syringes may be stored at room temperature between 68°F to 77°F (20°C to 25°C) for up to 48 hours but must be used or discarded within 48 hours of removal from the refrigerator.  

• Do not freeze or shake. 

Coadministration with Routine Childhood Vaccines   

Enflonsia (clesrovimab) may be given at the same time as routine childhood vaccines, (including live vaccines such as MMR and Varicella) with no need for interval spacing. Simultaneous administration is acceptable. 

MIP's Respiratory Season Lunch and Learn Webinar Q&A 

Thank you to everyone who attended the Maine Immunization Program's Annual Respiratory Season Lunch and Learn Webinar on Wednesday, September 24.  We received many great questions during the session and providing the Q&A below.     

 For those unable to join, the presentation slides are available on our website.  

 Q: Is the RSV maternal vaccine, Abrysvo, administered as a one-time dose or given during subsequent pregnancy?  

• It is currently not recommended that pregnant patients who received the maternal RSV vaccine during their last pregnancy receive an additional dose during a subsequent pregnancy. Clinicians should review the patient’s medical record to confirm vaccination status. For patients vaccinated in a previous pregnancy, their infants should receive a monoclonal antibody.    
• Maternal Respiratory Syncytial Virus Vaccination | ACOG   

Q: If a mom received the RSV vaccine in January and the baby is born in March- does the baby qualify for a dose entering the season since they aren't covered past 6 months?  

• No, the baby is considered protected from RSV if Abrysvo was administered to the mother at 32-36 weeks' gestation.  Maternal antibodies protect the baby against RSV for approximately 6 months after birth.   

• For infants born outside of the seasonal administration window (which is April through September) and for young children who are at increased risk for severe RSV disease and entering their second RSV season, the optimal timing for infant RSV antibody administration is shortly before the RSV season begins (e.g., October or November).    

Q: Is there any difference in side effect profiles for the new RSV monoclonal antibody, Enflonsia (clesrovimab)?   

• The most common adverse reactions were injection-site erythema (3.8%), injection-site swelling (2.7%), and rash (2.3%). 

• Do not administer ENFLONSIA to infants with a history of serious hypersensitivity reactions, including anaphylaxis, to any component of ENFLONSIA.  

• Serious hypersensitivity reactions, including anaphylaxis, have been observed with other human immunoglobulin G1 (IgG1) monoclonal antibodies. If signs or symptoms of a clinically significant hypersensitivity reaction or anaphylaxis occur, initiate appropriate medications and/or supportive therapy.   

• ENFLONSIA™ (clesrovimab-cfor) | Official HCP Web Site   
• ENFLONSIA Prescribing Information   

Q: Is there any routine post immunization counseling on side effects for the new RSV monoclonal antibody, Enflonsia (clesrovimab)?   

• Merck provides a helpful patient information sheet explaining the use and potential side effects of Enflonsia (clesrovimab)    

Q: If a mother received Abrysvo for her first pregnancy, should her second child get Beyfortus? 

• Yes – maternal RSV (Abrysvo) is only indicated for one pregnancy.  Any future births, the infant would receive an RSV monoclonal antibody (either nirsevimab or clesrovimab).   

Q: If we have Beyfortus from last year that will expire before the 1st of October, we can’t give it, correct? Are there any thoughts about extending the season as we are already seeing it?  

• Do not administer nirsevimab past the expiration date.   Ensure doses have been stored properly and nirsevimab may be given up until the expiration date.     

• Nirsevimab dose expiration dates will not be extended.  Please return any expired doses following the returns module in ImmPact.    

 Best Practices for RSV Season   

Educating patients about the best practices for patient care during respiratory illnesses will provide patients with a full set of tools to keep themselves and their families safe from respiratory diseases this season.  

Resources:    

• Now FDA-Approved ENFLONSIA™ (clesrovimab-cfor) 105 mg Injection | Official Consumer Site 
• AAP Recommendations for the Prevention of RSV Disease in Infants and Children | Red Book Online | American Academy of Pediatrics 
• RSV Immunization Guidance for Infants and Young Children | RSV | CDC 
• Maternal Respiratory Syncytial Virus Vaccination | ACOG 
• Respiratory Syncytial Virus (RSV) Prevention