
Originally Posted by
"The New England Journal of Medicine
Vaccine effectiveness was lower for the omicron variant than for the delta variant at all intervals after vaccination and for all combinations of primary courses and booster doses investigated. Among those who had received two ChAdOx1 nCoV-19 doses, almost no protective effect of vaccination against symptomatic disease caused by the omicron variant was noted from 20 to 24 weeks after the second dose. Among those who had received two BNT162b2 doses, vaccine effectiveness was 65.5% (95% CI, 63.9 to 67.0) 2 to 4 weeks after the second dose, dropping to 15.4% (95% CI, 14.2 to 16.6) after 15 to 19 weeks and dropping further to 8.8% (95% CI, 7.0 to 10.5) after 25 or more weeks. The vaccine effectiveness of two doses of mRNA-1273 vaccine had a similar reduction over time from 75.1% (95% CI, 70.8 to 78.7) after 2 to 4 weeks to 14.9% (95% CI, 3.9 to 24.7) after 25 or more weeks. Among persons who received ChAdOx1 nCoV-19 as the primary course, from 2 to 4 weeks after a BNT162b2 booster dose, vaccine effectiveness increased to 62.4% (95% CI, 61.8 to 63.0) before waning to 39.6% (95% CI, 38.0 to 41.1) after 10 or more weeks. The mRNA-1273 booster vaccine increased effectiveness to 70.1% (95% CI, 69.5 to 70.7) after 2 to 4 weeks. This waned to 60.9% (95% CI, 59.7 to 62.1) after 5 to 9 weeks. Vaccine effectiveness was lowest among those who received a ChAdOx1 nCoV-19 primary course with a ChAdOx1 nCoV-19 booster vaccine. Waning efficacy was most notable against the omicron variant, for which the vaccine effectiveness was 46.7% (95% CI, 34.3 to 56.7) at 5 to 9 weeks. Among persons who received BNT162b2 as the primary course, from 2 to 4 weeks after a BNT162b2 booster dose, vaccine effectiveness increased to 67.2% (95% CI, 66.5 to 67.8) before declining to 45.7% (95% CI, 44.7 to 46.7) after 10 or more weeks. The mRNA-1273 booster increased vaccine effectiveness to 73.9% (95% CI, 73.1 to 74.6) after 2 to 4 weeks before decreasing to 64.4% (95% CI, 62.6 to 66.1) after 5 to 9 weeks. After an mRNA-1273 primary course, vaccine effectiveness increased to 64.9% (95% CI, 62.3 to 67.3) at 2 to 4 weeks after a BNT162b2 booster and 66.3% (95% CI, 63.7 to 68.8) at 2 to 4 weeks after an mRNA-1273 booster.