Clinical severity of, and effectiveness of mRNA vaccines against, covid-19 from omicron, delta, and alpha SARS-CoV-2 variants in the United States: prospective observational study.
BMJ. 2022 Mar 9;376:e069761. doi: 10.1136/bmj-2021-069761.
BMJ. 2022.
PMID: 35264324
Free PMC article.