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Infant RSV
Bridging the Gaps in Infant RSV Protection: FAQs

Released: November 04, 2025

Joseph Domachowske
Joseph Domachowske, MD
Sharon G. Humiston
Sharon G. Humiston, MD, MPH
Pablo J. Sanchez
Pablo J. Sanchez, MD
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Key Takeaways
  • A precise maternal RSV vaccine history is essential for determining infant eligibility for long-acting monoclonal antibodies.
  • The “start” of RSV season is regionally variable and should be informed by local epidemiology, not rigid dates or insurance restrictions.
  • Infants who contract RSV early in the season may still benefit from long-acting monoclonal antibody prophylaxis afterward.

At a recent symposium, expert faculty answered questions on infant immunization for respiratory syncytial virus (RSV). Here we explore answers to some of the most important questions.

When maternal RSV vaccination status is unclear or undocumented, what key factors should healthcare professionals consider in determining an infant's protection status?
As we bring long-acting monoclonal antibodies and maternal RSV vaccination into routine pediatric care, we would caution everyone to take a clear and comprehensive maternal history to avoid uncertainty around whether the infant should receive a long-acting RSV monoclonal antibody. This step is essential, as mothers may not know if or when they received the maternal RSV vaccine.

For families that are not planning to have their infant receive a long-acting RSV monoclonal antibody, the American College of Obstetricians and Gynecologists (ACOG) recommends a single dose of the maternal bivalent RSVpreF vaccine using seasonal administration to prevent RSV lower respiratory tract infection in infants. This one-time vaccination only applies to people who do not have a planned delivery within 2 weeks and are between 32 0/7 and 36 6/7 weeks of gestation. Infants born fewer than 14 days after maternal RSV vaccination are recommended to be immunized with a long-acting RSV monoclonal antibody after birth to ensure adequate protection.

ACOG also recommends several other vaccines during pregnancy, including COVID, Tdap, and flu. The number of vaccines leads to a fair amount of confusion regarding which vaccinations were received. Having patients check their MyChart can be a useful strategy. You can also get clarity by asking questions like “Which vaccines did you get?”, “Did you get the RSV vaccine?”, and “On what day did you get the RSV vaccine?”

For example, one of us once treated a mother who told us she had received “all the vaccines” that her obstetrician recommended. But after asking her to check with her obstetrician, it turned out that her obstetrician did not offer the RSV vaccine. Without the specifics of her vaccination history, it could have been mistakenly assumed that her infant was protected.

Situations like this underscore the importance of knowing the history. Ultimately, it is imperative that we never assume maternal vaccination. Instead, we must be certain about whether and when the maternal RSV vaccine was received when determining protection status of an infant before RSV season.

We also need to be sure of the date the mother received the maternal vaccine. If the maternal vaccination occurred too recently (fewer than 14 days before birth), that is not enough time for maximum transfer of antibody, and the infant is considered unprotected against RSV. If the mother’s vaccination date is unknown, then you should assume the infant is not protected. In these cases, a long-acting monoclonal antibody should be administered. 

Finally, RSV vaccination during a previous pregnancy does not protect through later pregnancies. If the mother received RSV vaccine during a previous pregnancy, then long-acting monoclonal antibody for infant protection is also indicated.

How do we identify the earliest date for administration of a preventive long-acting monoclonal antibody to ensure optimal protection and insurance coverage?
Long-acting RSV monoclonal antibodies are most effective when administered just before or at the start of the RSV season. The CDC definition of RSV season is when at least 3% of respiratory samples test positive for RSV. Practically, this includes October 1 through March 31 in most of the continental US or as determined by regional experts or health authorities.

US states and territories with very different weather patterns from the continental United States (eg, Alaska, and areas with tropical weather patterns, such as Hawaii, Southern Florida, Puerto Rico, and other island territories) may experience very different patterns of local RSV circulation. Thus, public health authorities in those areas may issue different recommendations for appropriate timing of RSV prevention strategies. That is, RSV season can be very different from region to region across the US, and it is essential to work with local laboratories and public heath teams to know your local and regional epidemiology.

For example, in Columbus, Ohio, we consider the start to be November 1st, so we aim to administer the long-acting monoclonal antibody in October for RSV prevention in infants.

In terms of insurance, we have found that most claims are accepted even if the vaccine is given a few days earlier than the official start of the RSV season, recognizing that coverage would be required the following week regardless.

The end of the RSV season is also determined by regional variance. One practice in Ohio stops administering the long-acting monoclonal antibody after March 31st whereas in Texas, local epidemiology defines the season as ending by late February, and in regions such as Hawaii or Southern Florida, prophylaxis is needed year round.

If an infant has already had an RSV infection, should they still receive a long-acting monoclonal antibody, and how soon after infection can it be given safely?
Even if an infant has an RSV infection early in the season (for example, in September), they still face the possibility of reinfection later in the same season. Therefore, if the infant is eligible to receive a long-acting monoclonal antibody, it should still be administered according to American Academy of Pediatrics or CDC recommendations.

Regarding how soon immunization can occur following infection, there is usually no need to delay. When an infant is hospitalized for RSV infection, we typically give the long-acting monoclonal antibody at the time of discharge if they are eligible.

Your Thoughts
How have you managed situations where unclear maternal vaccine records or confusing definitions of RSV season led to missed or delayed protection for infant? Leave a comment below to join the conversation.

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