What do medical sources say about RSV Vaccine (Abrysvo) (Abrysvo) during pregnancy?

1st Trimester: The FDA label indicates Abrysvo at 32 to 36 weeks, and the CDC lists September through January for most of the continental United States. CDC and ACOG place maternal vaccination in a late-pregnancy window, not in the first trimester. The main trial began at 24 weeks, and the label says use before 24 weeks has not been studied. MotherToBaby says studies have not assessed whether Abrysvo changes miscarriage risk, so later-pregnancy results do not answer that question. Ask your provider about your situation. 2nd Trimester: CDC recommends Abrysvo at 32 to 36 weeks and lists September through January for most of the continental United States; ACOG and SMFM extend the 2026 seasonal window through March 1. The FDA label reports a numerical preterm-birth imbalance in trials but says the evidence cannot establish or exclude a cause-and-effect link. A large French cohort and a US Vaccine Safety Datalink study did not find a significant increase in preterm birth. The VSD study and a 2026 review found a small blood-pressure-disorder signal, while another 2026 review found no overall preterm-birth increase but did find a signal in the trial subgroup. Ask your provider about your situation. 3rd Trimester: The FDA label and CDC page updated October 7, 2026, use weeks 32 to 36; CDC lists September through January for most of the continental United States. ACOG's September 2 schedule and SMFM's September 10 update extend the US seasonal window through March 1, while UKHSA offers the vaccine year-round from week 28 and EMA product information lists weeks 24 to 36. AAP's infant guidance focuses on antibody protection and says an infant born less than 14 days after maternal vaccination receives infant immunization, rather than setting a separate maternal-week window. The FDA label reports a numerical preterm-birth imbalance but says the data cannot establish or exclude a causal link; later studies show mixed results for blood-pressure disorders. FDA's January 2025 GBS warning is based on a postmarketing study among adults 65 and older; MHRA said no increased risk had been identified in pregnant recipients as of July 2025. Ask your provider about your situation.

What do medical sources say about RSV Vaccine (Abrysvo) (Abrysvo) while breastfeeding?

LactMed says breastfeeding is not a contraindication to this non-live vaccine, and CDC's general guidance says vaccines usually do not affect breastfeeding. LactMed and the FDA label report no published milk-level, infant-effect, or milk-production data for Abrysvo; MotherToBaby says studies in breastfeeding people have not been done. ACOG's 2026 FAQ says antibodies pass through human milk and protect babies for six months, while SMFM says breastfeeding and infant protection through milk were not evaluated. These statements differ because direct Abrysvo-specific milk and infant data are absent, so a milk benefit has not been established in a human study. Ask your provider about your situation.

Where do sources disagree on RSV Vaccine (Abrysvo) (Abrysvo) in pregnancy or breastfeeding?

What gestational and calendar window applies to maternal RSV vaccination? CDC's pregnancy page, updated October 7, 2026, says weeks 32 through 36 and September through January for most of the continental United States. ACOG's 2026 schedule and FAQ and SMFM's September 2026 update use weeks 32 through 36 and extend the US seasonal window through March 1. The US agencies describe seasonal eligibility differently for the 2026 to 2027 season. The UK and European product information use different program structures and RSV-season assumptions, and AAP's FAQ focuses on infant immunization rather than setting a separate maternal-week schedule. The agencies agree that maternal vaccination is timed to late pregnancy, but their exact weeks and seasonal dates differ. Preserve the US CDC, ACOG, and SMFM dates with their source and date, and keep UK and EMA information separate rather than blending the schedules.

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RSV Vaccine (Abrysvo)

Everyday exposureVaccines

Abrysvo

Also called · 6 names▾

Abrysvo, RSV shot, RSV vaccine in pregnancy, respiratory syncytial virus vaccine, maternal RSV vaccine, RSV immunization

Protein-subunit vaccine

General information · effects depend on amount, timing, and how it is used. About these sources

Pregnancy

The MATISSE phase 3 trial enrolled pregnant participants at 24 to 36 weeks. Its published abstract reports vaccine efficacy of 81.8% against medically attended severe RSV lower-respiratory illness through 90 days after birth and 69.4% through 180 days, with no safety signals detected in mothers or children through age 24 months. These later-pregnancy findings do not establish outcomes from first-trimester use. The FDA label reports no evidence of a vaccine-associated increase in congenital anomalies or fetal deaths in its trial data, but notes that the studies were conducted at 24 to 36 weeks and that Abrysvo has not been studied before 24 weeks. MotherToBaby says studies have not assessed whether Abrysvo changes miscarriage risk. In the infant safety population, the FDA label reports preterm birth in 207 of 3,659 vaccine-group infants (5.7%) and 172 of 3,646 placebo-group infants (4.7%); it says the available data cannot establish or exclude a causal link. People at increased risk of preterm birth were generally excluded from trials. Recent evidence is mixed. A French national matched cohort compared 24,891 vaccinated with 24,891 unvaccinated pregnancies and found no significant increase in preterm birth, stillbirth, small-for-gestational-age birth, or preeclampsia. A 2026 US Vaccine Safety Datalink cohort included 13,966 vaccinated pregnancies and found no significant increase in preterm birth, stillbirth, or small-for-gestational-age birth, but reported hypertensive disorders in 17.3% versus 15.0% (adjusted risk ratio 1.13, 95% CI 1.07 to 1.19). A separate sequential surveillance study of 13,619 exposed pregnancies found no preterm-birth association, but said potential increases in hypertensive disorders, premature rupture of membranes, and preterm premature rupture could not be ruled out because confounding control was limited. A 2026 meta-analysis of nine studies (148,267 participants) found a small overall hypertensive-disorder association (RR 1.08, 95% CI 1.02 to 1.13), driven mainly by observational studies; its randomized-trial estimate was not significant, and the association was attributable to gestational hypertension rather than preeclampsia or eclampsia. A separate 2026 preterm-birth meta-analysis found an increased estimate in its randomized-trial subgroup (RR 1.26, 95% CI 1.08 to 1.46), no association in observational studies, and no overall association (RR 0.96, 95% CI 0.68 to 1.38); certainty was low to very low. A September 2026 review reported that the preterm-birth signal was not robustly significant for licensed Pfizer use in the 32 to 36 week window, but its screening and extraction used a single reviewer with language-model-assisted verification.

Breastfeeding

LactMed's May 2026 record says breastfeeding is not a contraindication to RSV vaccination and that non-live vaccines are generally considered acceptable during breastfeeding. It reports no relevant published information on RSV vaccine levels in milk, infant levels, effects in breastfed infants, or effects on lactation and breastmilk. The FDA label states that it is not known whether Abrysvo is excreted in human milk and that data are unavailable to assess effects on a breastfed infant or milk production. MotherToBaby likewise says studies have not been done in people who are breastfeeding. CDC guidance supports vaccination in breastfeeding at the general vaccine-class level. ACOG's September 2026 FAQ states that antibodies pass through human milk and protect babies during the first six months, while SMFM's September 2026 statement says lactation and infant protection through breastmilk were not evaluated. No direct Abrysvo milk-transfer or breastfed-infant outcome study was identified in the reviewed sources.

What gestational and calendar window applies to maternal RSV vaccination?

Source A says: CDC's pregnancy page, updated October 7, 2026, says weeks 32 through 36 and September through January for most of the continental United States. (CDC: Vaccine Recommendations Before, During, and After Pregnancy)
Source B says: ACOG's 2026 schedule and FAQ and SMFM's September 2026 update use weeks 32 through 36 and extend the US seasonal window through March 1. (ACOG: 2026 Maternal Immunization Schedule, ACOG: The RSV Vaccine and Pregnancy, SMFM Statement: Respiratory Syncytial Virus Vaccination in Pregnancy, 2026 update)
Why they differ: The US agencies describe seasonal eligibility differently for the 2026 to 2027 season. The UK and European product information use different program structures and RSV-season assumptions, and AAP's FAQ focuses on infant immunization rather than setting a separate maternal-week schedule.
Other sources: UKHSA offers maternal vaccine from week 28 throughout the year, while EMA product information lists weeks 24 to 36. AAP discusses infant antibody use, including the less-than-14-day interval between maternal vaccination and birth. (UKHSA: RSV vaccination of pregnant women for infant protection, EMA: Abrysvo European Public Assessment Report, AAP: RSV Immunization Administration Frequently Asked Questions)
What the evidence shows overall: The agencies agree that maternal vaccination is timed to late pregnancy, but their exact weeks and seasonal dates differ. Preserve the US CDC, ACOG, and SMFM dates with their source and date, and keep UK and EMA information separate rather than blending the schedules.

Do current studies show an increased risk of preterm birth?

Source A says: The FDA label reports a numerical preterm-birth imbalance and says the available data cannot establish or exclude a causal relationship. A 2026 meta-analysis found an increase in its randomized-trial subgroup, although that analysis included trials beyond the licensed Pfizer window. (DailyMed: Abrysvo prescribing information, Pfizer, SPL version 15, Leskinen et al., Immunity, Inflammation and Disease 2026: preterm birth meta-analysis)
Source B says: The 2026 French cohort, the 2026 Vaccine Safety Datalink cohort, and sequential surveillance found no significant preterm-birth increase; a 2026 review found no robustly significant increase for licensed Pfizer use at 32 to 36 weeks. (Gabet et al., Obstetrics & Gynecology 2026: French maternal and neonatal outcomes cohort, Vaccine Safety Datalink study of RSVpreF during pregnancy, 2026, Michnick et al., JAMA Network Open 2026: sequential RSVpreF safety surveillance, Kucukbas Ozonder and Yavuz, Frontiers in Public Health 2026: maternal RSV vaccine systematic review)
Why they differ: The randomized-trial meta-analysis included a GSK vaccine trial and wider gestational timing, while post-approval cohorts mostly studied vaccination in the licensed window. Cohort results can also vary with comparator choice and confounding control; the sequential-surveillance paper says some obstetric signals could not be ruled out for this reason.
What the evidence shows overall: The FDA's numerical imbalance remains relevant, but it does not prove that the vaccine caused preterm birth. Large later cohorts did not find a significant increase within current practice, and the 2026 reviews reach different estimates. Keep the uncertainty visible rather than describing the risk as absent or established.

Are hypertensive disorders of pregnancy associated with RSVpreF vaccination?

Source A says: The 2026 Vaccine Safety Datalink study reported hypertensive disorders in 17.3% of vaccinated pregnancies and 15.0% of matched unvaccinated pregnancies (aRR 1.13). The 2026 meta-analysis found a small pooled association, driven mainly by observational studies, and sequential surveillance could not rule out a signal. (Vaccine Safety Datalink study of RSVpreF during pregnancy, 2026, Alami et al., Vaccine 2026: hypertensive disorders of pregnancy meta-analysis, Michnick et al., JAMA Network Open 2026: sequential RSVpreF safety surveillance)
Source B says: The 2026 French cohort found no significant increase in preeclampsia, and the randomized-trial subgroup in the 2026 meta-analysis was not statistically significant. (Gabet et al., Obstetrics & Gynecology 2026: French maternal and neonatal outcomes cohort, Alami et al., Vaccine 2026: hypertensive disorders of pregnancy meta-analysis)
Why they differ: The studies use different definitions, including a broad hypertensive-disorder composite versus preeclampsia alone. Observational studies can retain confounding, while randomized trials may have too few events to detect a small difference.
What the evidence shows overall: Recent evidence includes a small observational association, but the randomized-trial estimate was not significant and the French cohort did not find increased preeclampsia. The studies do not establish that vaccination causes hypertensive disorders.

Does Abrysvo provide a demonstrated benefit to a breastfed infant through human milk?

Source A says: ACOG's public FAQ says antibodies pass into human milk and protect babies from RSV for the first six months after birth. SMFM says additional infant protection is expected, though it also notes the data were not evaluated. (ACOG: The RSV Vaccine and Pregnancy, SMFM Statement: Respiratory Syncytial Virus Vaccination in Pregnancy, 2026 update)
Source B says: The FDA label says it is not known whether Abrysvo is excreted in human milk and that infant and milk-production data are unavailable. LactMed and MotherToBaby report no relevant published Abrysvo milk or breastfed-infant data; SMFM says this question was not evaluated. (DailyMed: Abrysvo prescribing information, Pfizer, SPL version 15, LactMed: Respiratory Syncytial Virus Vaccine, MotherToBaby: Respiratory Syncytial Virus (RSV) Vaccine (Abrysvo), SMFM Statement: Respiratory Syncytial Virus Vaccination in Pregnancy, 2026 update)
Why they differ: The public FAQ presents antibody transfer as a benefit, while the product label and evidence summaries describe the absence of direct Abrysvo-specific milk and infant studies. General vaccine-class guidance about breastfeeding does not measure antibody transfer or infant outcomes for this product.
Other sources: CDC's general guidance says vaccination usually does not affect breastfeeding, but it does not establish a milk-mediated benefit for Abrysvo specifically. (CDC: Special Situations, Breastfeeding and Vaccination)
What the evidence shows overall: General compatibility during breastfeeding is supported by class-level guidance. Direct Abrysvo-specific milk transfer and infant-effect evidence was not found, so describe the claimed milk benefit as expected or uncertain rather than as an observed outcome.

Last reviewed 2026-10-14

Independent check 2026-10-14

Not yet clinician-reviewed

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Flu Vaccine
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RSV Vaccine (Abrysvo)

RSV Vaccine (Abrysvo) — Breastfeeding

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