Tracking COVID-19 vaccine effectiveness over the first 9 months

Embargoed until: Publicly released: 2022-01-13 09:00

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mRNA vaccines Pfizer and Moderna protect against COVID-19 infection with 94.5 per cent and 95.9 per cent respectively after two months, before dropping to 66.6 per cent and 80.3 per cent at seven months, according to US research. The team used North Carolina COVID-19 surveillance data to estimate vaccine outcomes for about 10 million people from December 2020 to September 2021. The researchers say the emergence of Delta in mid-2021 accounts for part of the waning effectiveness of the vaccines, with Pfizer effectiveness dropping 15 per cent and Moderna 10 per cent as the variant took over. Both vaccines, along with Johnson & Johnson/Janssen, maintained better effectiveness against severe illness over time compared to protection against infection, they add.