Interim Estimates of Vaccine Effectiveness of BNT162b2 and mRNA-1273 COVID-19 Vaccines in Preventing SARS-CoV-2 Infection Among Health Care Personnel, First Responders, and Other Essential and Frontline Workers — Eight U.S. Locations, December 2020–March 2021

Thompson, Mark G.; Burgess, Jefferey L.; Naleway, Allison L.; Tyner, Harmony L.; Yoon, Sarang K.; Meece, Jennifer; Olsho, Lauren E.W.; Caban-Martinez, Alberto J.; Fowlkes, Ashley; Lutrick, Karen; Kuntz, Jennifer L.; Dunnigan, Kayan; Odean, Marilyn J.; Hegmann, Kurt T.; Stefanski, Elisha; Edwards, Laura J.; Schaefer-Solle, Natasha; Grant, Lauren; Ellingson, Katherine; Groom, Holly C.; Zunie, Tnelda; Thiese, Matthew S.; Ivacic, Lynn; Wesley, Meredith G.; Lamberte, Julie Mayo; Sun, Xiaoxiao; Smith, Michael E.; Phillips, Andrew L.; Groover, Kimberly D.; Yoo, Young M.; Gerald, Joe; Brown, Rachel T.; Herring, Meghan K.; Joseph, Gregory; Beitel, Shawn; Morrill, Tyler C.; Mak, Josephine; Rivers, Patrick; Harris, Katherine M.; Hunt, Danielle R.; Arvay, Melissa L.; Kutty, Preeta; Fry, Alicia M.; Gaglani, Manjusha

Messenger RNA (mRNA) BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna) COVID-19 vaccines have been shown to be effective in preventing symptomatic COVID-19 in randomized placebo-controlled Phase III trials (1,2); however, the benefits of these vaccines for preventing asymptomatic and symptomatic SARS-CoV-2 (the virus that causes COVID-19) infection, particularly when administered in real-world conditions, is less well understood. Using prospective cohorts of health care personnel, first responders, and other essential and frontline workers* in eight U.S. locations during December 14, 2020-March 13, 2021, CDC routinely tested for SARS-CoV-2 infections every week regardless of symptom status and at the onset of symptoms consistent with COVID-19-associated illness. Among 3,950 participants with no previous laboratory documentation of SARS-CoV-2 infection, 2,479 (62.8%) received both recommended mRNA doses and 477 (12.1%) received only one dose of mRNA vaccine.†Among unvaccinated participants, 1.38 SARS-CoV-2 infections were confirmed by reverse transcription-polymerase chain reaction (RT-PCR) per 1,000 person-days.§ In contrast, among fully immunized (≥14 days after second dose) persons, 0.04 infections per 1,000 person-days were reported, and among partially immunized (≥14 days after first dose and before second dose) persons, 0.19 infections per 1,000 person-days were reported. Estimated mRNA vaccine effectiveness for prevention of infection, adjusted for study site, was 90% for full immunization and 80% for partial immunization. These findings indicate that authorized mRNA COVID-19 vaccines are effective for preventing SARS-CoV-2 infection, regardless of symptom status, among working-age adults in real-world conditions. COVID-19 vaccination is recommended for all eligible persons.