Boosters or previous COVID-19 infection are needed to prevent symptomatic Omicron

Embargoed until: Publicly released: 2022-06-16 07:00

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Two doses of an mRNA COVID-19 vaccine has a negligible effect on the risk of symptomatic Omicron but previous infections and booster doses change this, according to international research. The team looked at infection rates in Qatar to compare rates among unvaccinated, double vaccinated and triple vaccinated people in the Omicron era, and look at how well previous COVID-19 infection protects against the now-dominant variant. Previous infection alone was 46.1% effective against symptomatic Omicron, triple vaccination was 52.2%, double vaccination and prior infection was 55.1% and triple vaccination and prior infection was 77.3%.