The efficacy of the 3rd dose against hospitalizations was measured at 90% in the event of infection with the Omicron variant
Vaccines and booster doses against Covid-19 continued to have very high efficacy against severe cases of the disease during the surge caused by the Omicron variant, according to the US Centers for Disease Prevention and Control study (CDC) which reviews data from more than 300,000 emergency room visits, urgent care clinics and hospitalizations in 10 states from August 26, 2021 to January 5, 2022.
During the period when the Delta variant was dominant, vaccine efficacy against Covid-19 hospitalizations was 90% between 14 and 179 days after the second dose of a vaccine. It fell to 81% more than 180 days after the second dose and rose to 94% 14 or more days after the third.
Once Omicron became dominant, the efficacy of the vaccine against hospitalizations between 14 and 179 days after the second dose was estimated at 81%; it was 57% after more than 180 days after the second dose, and 90% 14 days or more after the third.
But falling effectiveness against infections
A second study, based on data from 25 US states and local jurisdictions, shows that vaccine effectiveness against infections increased from 93% before Delta to about 80% once Delta became dominant; but death protection remained stable – and high – at 94%.
Efficacy against infections dropped to 68% with Omicron. The authors were unable to derive an estimate of vaccine protection against death during Omicron due to a delay in recording information, but scientists widely expect it to remain. very high.
The study also shows that during the Delta wave, unvaccinated people were 16 times more likely to die. And unvaccinated people were 50 times more likely to die from Covid than vaccinated people who received a booster.