Källa:
https://www.medrxiv.org/content/10.1101/2021.12.20.21267966v3
Se även:
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)02243-1/fulltext
https://www.cdc.gov/mmwr/volumes/70/wr/mm7031e2.htm
https://www.medrxiv.org/content/10.1101/2021.07.31.21261387v1
https://www.medrxiv.org/content/10.1101/2021.07.31.21261387v6