• Mark G Thompson, Jefferey L Burgess, Allison L Naleway, Harmony L Tyner, Sarang K Yoon, Jennifer Meece, Olsho Lauren E W LEW, Alberto J Caban-Martinez, Ashley Fowlkes, Karen Lutrick, Jennifer L Kuntz, Kayan Dunnigan, Marilyn J Odean, Kurt T Hegmann, Elisha Stefanski, Laura J Edwards, Natasha Schaefer-Solle, Lauren Grant, Katherine Ellingson, Holly C Groom, Tnelda Zunie, Matthew S Thiese, Lynn Ivacic, Meredith G Wesley, Julie Mayo Lamberte, Xiaoxiao Sun, Michael E Smith, Andrew L Phillips, Kimberly D Groover, Young M Yoo, Joe Gerald, Rachel T Brown, Meghan K Herring, Gregory Joseph, Shawn Beitel, Tyler C Morrill, Josephine Mak, Patrick Rivers, Katherine M Harris, Danielle R Hunt, Melissa L Arvay, Preeta Kutty, Alicia M Fry, and Manjusha Gaglani.
• MMWR Morb. Mortal. Wkly. Rep. 2021 Apr 2; 70 (13): 495-500.

AbstractMessenger 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.

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