Abrysvo (respiratory syncytial virus vaccine)

Preterm Births in Study 1 and Study 2

A numerical imbalance in preterm births in ABRYSVO recipients compared to placebo recipients was observed in both Studies 1 and 2. In Study 2, preterm births occurred in 5.3% (6 out of 114) in the ABRYSVO group and 2.6% (3 out of 116) in the placebo group. In the subsequent Study 1, preterm birth events occurred in 5.7% [95% CI: 4.9, 6.5] (207 out of 3,659) in the ABRYSVO group and 4.7% [95% CI: 4.1, 5.5] (172 out of 3,646) in the placebo group. In infants born preterm, 84 infants in the ABRYSVO group and 81 infants in the placebo group remained hospitalized or were readmitted to the hospital in the neonatal period (up to 30 days after birth). Available data are insufficient to establish or exclude a causal relationship between preterm birth and ABRYSVO.

A numerical imbalance in preterm births was also observed in Study 1 among the subgroup of infants born to participants who were vaccinated at 32 through 36 weeks gestation, with 4.3% (71/1,667) in the ABRYSVO group and 3.7% (60/1,640) in the placebo group.

Adverse Reactions in Infants

In Study 1, adverse events in infants from birth to 1 month of age were observed in 38.0% in the ABRYSVO group compared to 35.4% in the placebo group. Low birth weight was observed in 5.1% of participants in the ABRYSVO group versus 4.3% in the placebo group, and neonatal jaundice was observed in 7.3% in the ABRYSVO group versus 6.9% in the placebo group.

Serious Adverse Events in Study 1

In Study 1, serious adverse events in maternal participants were reported by 16.6% in the ABRYSVO group and 15.8% in the placebo group occurring any time during the study (see Table 3) with 4.3% serious adverse events in the ABRYSVO group and 3.8% in the placebo group occurring within 1 month after vaccination. Most of the serious adverse events in maternal participants were related to pregnancy complications and occurred after the 1 month period following vaccination.

Within 30 days after vaccination, atrial fibrillation was reported in 11 vaccine recipients and 3 placebo recipients (of which 5 in the ABRYSVO group and 2 in the placebo group were serious adverse events); the onset of symptoms was 18 to 30 days post vaccination. The currently available information on atrial fibrillation is insufficient to determine a causal relationship to the vaccine [see Use in Specific Populations (8.6)]. Within 14 days of vaccination, lymphadenopathy was reported in 6 vaccine recipients, considered related to ABRYSVO, and 3 placebo recipients. There were no other notable patterns or numerical imbalances between groups for specific categories of unsolicited adverse events.

Serious Adverse Events in Study 3

In Study 3, SAEs were reported by 6.2% of participants in the ABRYSVO group and 6.1% in the placebo group. Three participants in the ABRYSVO group had SAEs which were assessed as possibly related to study vaccination: Guillain‑Barré syndrome reported 7 days after vaccination (with diagnosis later revised to chronic inflammatory demyelinating polyneuropathy), Miller Fisher syndrome reported 8 days after vaccination, and hypersensitivity reported 8 hours after vaccination.

Solicited local and systemic reactions had a median duration of 1-2 days.

Unsolicited Adverse Events in Study 4

Unsolicited adverse events occurring within 1 month after vaccination were reported in 7.1% and 7.6% of participants who received ABRYSVO and placebo, respectively. One case of urticaria occurred on the same day as vaccine administration and was considered related to ABRYSVO.

Serious Adverse Events in Study 4

In Study 4, SAEs were reported by 1.1% of participants in the ABRYSVO group and 3.1% in the placebo group. No SAEs were assessed as related to study vaccination.

Serious Adverse Events Reported from Other Studies

Anaphylaxis was reported in a participant enrolled in a study (NCT06473519) in the US, with onset of symptoms 10 minutes after vaccination with ABRYSVO. The study enrolled healthy female participants 18 years through 49 years of age (n=450).

The following adverse reactions have been identified from spontaneous reports during postmarketing use of ABRYSVO. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to the vaccine.

Immune System Disorders: Anaphylaxis and other hypersensitivity reactions including rash and urticaria.

Nervous System Disorders: Guillain‑Barré syndrome.

Postmarketing Observational Study of the Risk of Guillain‑Barré Syndrome following Vaccination with ABRYSVO

The association between vaccination with ABRYSVO and Guillain‑Barré syndrome (GBS) was evaluated among Medicare beneficiaries 65 years of age and older. [...] The analyses of all GBS cases based on claims data suggest an increased risk of GBS during the 42 days following vaccination with ABRYSVO, with an incidence rate ratio (GBS cases in the risk window/control window) of 2.02 (95% CI: 0.93, 4.40) and an estimated 9 excess cases of GBS per million doses administered to individuals 65 years of age and older. [...] While the results of this observational study suggest an increased risk of GBS with ABRYSVO, available evidence is insufficient to establish a causal relationship.

Side effects that have been reported with the RSV Vaccine include:
pain, bruising, redness or swelling at the site of injection
fever, headache, muscle or joint pain
Some side effects can be serious. If you experience any of these symptoms, call your doctor immediately or get emergency medical treatment:
numbness in the extremities, muscle pain, difficulty walking or standing, paralysis
rash, shortness of breath or difficulty breathing, swelling of face or throat

People sometimes faint after medical procedures, including vaccination. Tell your provider if you feel dizzy or have vision changes or ringing in the ears.

Adverse reactions should be reported to the Vaccine Adverse Event Reporting System (VAERS). Your health care provider will usually file this report, or you can do it yourself. Visit https://vaers.hhs.gov or call 1-800-822-7967. VAERS is only for reporting reactions, and VAERS staff members do not give medical advice.