TABLE 3. Efficacy of 1 dose of Pfizer respiratory syncytial virus RSVpreF vaccine against respiratory syncytial virus–associated disease among adults aged ≥60 years — multiple countries, 2021–2023.
| Efficacy evaluation period | Vaccine efficacy against outcome, % (95% CI)* | |
|---|---|---|
| RSV-associated LRTD† | RSV-associated medically attended LRTD§ | |
| Season 1¶ | 88.9 (53.6–98.7) | 84.6 (32.0–98.3) |
| Season 2 (interim)** | 78.6 (23.2–96.1) | —†† |
| Combined seasons 1 and 2 (interim)§§ | 84.4 (59.6–95.2) | 81.0 (43.5–95.2) |
Abbreviations: LRTD = lower respiratory tract disease; LRTI = lower respiratory tract illness; RSV = respiratory syncytial virus.
* Manufacturer-calculated efficacy. Includes events >14 days after injection and person-time available from the manufacturer’s pivotal phase 3 trial. Estimates are unadjusted.
† The RSVpreF trial had two co-primary endpoints, defined as RSV LRTI with two or more lower respiratory signs or symptoms lasting >1 day, and RSV LRTI with three or more lower respiratory signs or symptoms lasting >1 day. Lower respiratory signs and symptoms included new or worsened cough, sputum production, wheezing, shortness of breath, and tachypnea. For RSVpreF estimates in this report, LRTD refers to the RSVpreF trial endpoint of RSV LRTI with three or more lower respiratory signs or symptoms.
§ Medically attended RSV-associated LRTD was defined as LRTD prompting any health care visit (any outpatient or inpatient visit such as hospitalization, emergency department visit, urgent care visit, home health care services, primary care physician office visit, pulmonologist office visit, specialist office visit, other visit, or telehealth contact). Estimates were not included in per-protocol assessments.
¶ Season 1 vaccine efficacy estimates reflect efficacy against first events occurring during the first complete RSV season for Northern and Southern Hemisphere participants (August 2021–October 2022; exact study-defined season dates were site-dependent).
** Season 2 (interim) vaccine efficacy estimates reflect efficacy against first events occurring during the second complete RSV season for Northern Hemisphere participants only (July 2022–January 2023; Southern Hemisphere data not yet available).
†† Interim analysis underpowered to estimate efficacy.
§§ Combined season 1 and 2 (interim) vaccine efficacy estimates reflect efficacy against first events occurring any time during season 1 or season 2. The mean time from start to end of efficacy surveillance was approximately 12 months per participant.