Pregnant patients in the United States are now navigating something that did not exist a year ago: two credible immunization schedules that do not match. And for the first time, they have hard numbers on infant hospitalizations to bring into that conversation.
Researchers at the University of Pittsburgh and UPMC reported in JAMA Network Open on June 5 that among infants younger than three months, maternal RSV vaccination was associated with roughly 68 percent effectiveness against hospitalization for RSV-related respiratory illness and about 69 percent effectiveness against more severe lower respiratory tract disease.
That finding lands in the middle of a guidance split. The American College of Obstetricians and Gynecologists released its own 2026 maternal immunization schedule in June, the first time the organization has published recommendations separate from federal ones. The schedule was endorsed by 13 medical and health organizations, including the American Academy of Pediatrics, the Infectious Diseases Society of America, and the Society for Maternal-Fetal Medicine, and it followed ACOG's withdrawal from the CDC's Advisory Committee on Immunization Practices in February 2026.
For an expectant parent, this is not an abstract governance dispute. It is the reason two clinicians can give different answers in the same week, and the reason a pharmacy and an obstetric practice may operate from different documents.
Numbers Parents Can Actually Use
The Pittsburgh study was built around a question families actually ask. It examined infants 90 days old or younger who were hospitalized for respiratory illness in western Pennsylvania across the 2023-2024 and 2024-2025 RSV seasons, comparing outcomes between those whose mothers received the RSVpreF vaccine during pregnancy and those whose mothers did not. Infants who received the separate monoclonal antibody after birth were excluded so the two approaches would not be confused.
"We designed this study to focus on what matters most to families," said lead author Anne-Marie Rick, MD, PhD, of Pitt School of Medicine and UPMC, in a UPMC statement.
The scale of the underlying problem gives those percentages meaning. RSV is the leading cause of infant hospitalization in the United States, and CDC figures cited by the research team indicate roughly two to three of every 100 babies younger than three months are hospitalized each year because of it. Severe cases can require oxygen support or mechanical ventilation.
A separate and larger analysis published in JAMA Pediatrics in March 2026, drawn from a seven-site CDC surveillance network, estimated that both the maternal RSV vaccine and the infant monoclonal antibody protected infants against RSV-associated hospitalization during the 2024-2025 season. That study was not industry-funded and reached a consistent conclusion, which strengthens the overall picture.
Two Schedules, One Appointment
The ACOG schedule lists four routinely recommended maternal vaccines: inactivated or recombinant influenza vaccine at any trimester, COVID-19 vaccine, Tdap preferably during weeks 27 through 36 of each pregnancy, and the maternal RSV vaccine between 32 weeks 0 days and 36 weeks 6 days of gestation.
The clearest point of divergence is COVID-19. ACOG continues to recommend COVID-19 vaccination during pregnancy; current CDC guidance does not carry the same recommendation. ACOG also specifies that the live attenuated intranasal influenza vaccine is not indicated during pregnancy, though it is acceptable after delivery.
ACOG has stated its position plainly. "It is well documented that respiratory conditions can cause poor outcomes during pregnancy," ACOG President Steven J. Fleischman, MD, MBA, said in an organizational statement.
On RSV specifically, the two approaches are complementary rather than competing. Clinical guidance holds that an infant generally needs one form of protection, not both. If the mother received the vaccine at least 14 days before delivery, the infant typically does not need the monoclonal antibody. If she was not vaccinated, or delivered within 14 days of vaccination, the infant should receive the antibody after birth during RSV season.
Timing is also seasonal. In most of the continental United States, the maternal RSV vaccine is given between September and January, which means patients due this fall are making the decision right now. Jurisdictions with different seasonality, including Alaska and some tropical territories, follow local guidance.
Reading the Study's Limits Alongside Its Findings
The funding and design details belong next to the headline number, not buried below it.
The JAMA Network Open study was funded by Pfizer Inc through a collaboration with the University of Pittsburgh, and Pfizer employees are among the co-authors. Rick reported receiving grant support from Pfizer during the study and personal fees plus a site principal investigator role for a Pfizer vaccine trial outside the submitted work. Several other Pitt and UPMC co-authors reported Pfizer grant support. Pfizer manufactures the RSVpreF vaccine that the study evaluated.
Beyond funding, the design carries real constraints. This was a retrospective case-control analysis using a test-negative design within a single health system in one region, not a randomized trial. Effectiveness estimates from one health system and one geography may not transfer cleanly to populations with different demographics, care patterns, or RSV circulation. The analysis covered infants 90 days or younger, so it does not speak to protection later in the first year.
The research team acknowledged those limits and is continuing the work. The study is part of an ongoing four-year effort that will follow the 2025-2026 and 2026-2027 seasons and extend the analysis to infants up to 180 days old, which should address how long protection lasts.
Preparing for the Obstetrician Conversation
The purpose of this data is to make the appointment more productive, not to settle the decision in advance. Vaccination during pregnancy is a personal medical decision that belongs with a qualified clinician who knows the individual history.
Patients can reasonably ask which schedule their practice is following and why, since the answer determines what they will be offered. They can ask about timing, particularly whether their due date and the 32 to 36 week RSV window line up, and what happens if delivery comes early. They can ask whether the infant monoclonal antibody is the better route in their situation, and confirm the 14-day threshold that determines which product the baby needs.
Insurance is worth raising directly. When professional society recommendations diverge from federal ones, coverage can follow the federal schedule, and patients should confirm with their plan rather than assume. Patients covered by Medicaid or receiving care at a federally qualified health center should ask what is stocked on site, since availability varies by practice and pharmacy.
Considerable uncertainty remains. Whether federal guidance will shift again, how insurers will handle the divergence through the coming respiratory season, and how long maternal antibody protection persists in infants are all unresolved. Updated CDC respiratory season guidance and the next round of surveillance data are expected before the fall season begins. MedicalDaily will track both.
Frequently Asked Questions
Why are pregnant patients getting different vaccine advice? ACOG released its own 2026 maternal immunization schedule in June, the first time it has diverged from federal recommendations, after withdrawing from the CDC advisory committee in February 2026.
What is the main difference between the schedules? ACOG continues to recommend COVID-19 vaccination during pregnancy. Current CDC guidance does not carry the same recommendation.
How effective was the RSV vaccine in the new study? Among infants younger than three months, maternal vaccination was associated with approximately 68 percent effectiveness against RSV hospitalization and 69 percent against more severe lung illness.
Who funded that research? Pfizer Inc funded the study through a collaboration with the University of Pittsburgh, and Pfizer employees co-authored it. Several academic authors reported Pfizer grant support.
Does a baby need the antibody shot if the mother was vaccinated? Generally no, if the mother was vaccinated at least 14 days before delivery. If she was not vaccinated, or delivered within 14 days, the infant should receive the monoclonal antibody during RSV season.
When during pregnancy is the RSV vaccine given? Between 32 weeks 0 days and 36 weeks 6 days of gestation, typically September through January in most of the continental United States.
What should patients ask their obstetrician? Which schedule the practice follows, how timing lines up with the due date, whether the infant antibody is preferable in their case, and how their insurance plan is handling the guidance difference.
