Study registration: *
Publication Thompson M, N Engl J Med, 2021
Dates: 2020-12-18 to 2021-06-22
Funding: Public/non profit (the Centers for Disease Control and Prevention)
Conflict of interest: Yes (Nicola Klein, grant/contract from GlaxoSmithKline, Merck, Pfizer, Protein Science, Sanofi Pasteur; Jill Ferdinands, travel assistance from Sanofi Pasteur; Allison Naleway, grant/contract from Pfizer; Suchitra Rao, grant/contract from BioFire Diagnostics, GlaxoSmithKline.)

Methods

Study design:Test-negative
Description of participants: Adults ≥50 years with Covid-19–like illness at multiple sites in the USA
Inclusion criteria:
  • Adults ≥50 years of age
  • Covid-19–like illness, defined as a clinical diagnosis of acute respiratory illness (e.g., Covid-19, respiratory failure, or pneumonia) or signs or symptoms (e.g., cough, fever, dyspnea, vomiting, or diarrhea) that have been associated with Covid-19 in previous studies
  • underwent molecular testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from January 1 to June 22, 2021
  • hospitalization lasting more than 24 hours

Exclusion criteria:
  • SARS-CoV-2–positive result on molecular or antigen assays more than 14 days before the index date (except for J&J results)
  • index dates occurred 1 to 13 days after the patient received the first dose of Covid-19 vaccine

Follow-up duration (months): 6.20
Vaccines:
  • 2 doses of BNT162b2
  • 2 doses of mRNA-1273
  • 1 dose of Ad26.COV2.S
  • 2 doses of BNT162b2 or mRNA-1273
Variant description :
Variant name: Alpha
Evidence: Indirect evidence (prevalence of variant in the population: 16-81%)
Documents
available

Protocol

Yes. In English

Statistical plan

Yes

Data-sharing stated: No
Data accessibility: Corresponding author: Dr. Thompson at isq8@cdc.gov
General comment In addition to the published report, the protocol and supplementary material were used in data extraction and risk of bias assessment. The average prevalence of variants was not reported; among variants of concern, Alpha comprised the largest subset during the study period across the regions sampled.

Some concerns over the possibility of uncontrolled confounding given the observational nature of the data and of outcome ascertainment being influenced by knowledge of vaccination status.