“Among those who had received 2 doses of [AstraZeneca], there was NO protective effect of vaccination against symptomatic disease with Omicron from 15 weeks after the second dose.”
Vaccine effectiveness against symptomatic disease by period after dose 2 and the booster dose is shown in Figure 1 and Table 2 for those who received a primary course of the ChAdOx1 or BNT162b2 vaccines. For both primary courses, the booster dose given was BNT162b2. Apart from 2-9 weeks post dose 2 for BNT162b2, effectiveness was lower for Omicron compared to Delta post vaccination at all time interval investigated.
Among those who had received 2 doses of AstraZeneca’s ChAdOx1, there was no protective effect of vaccination against symptomatic disease with Omicron from 15 weeks after the second dose. Among those who had received 2 doses of BNT162b2, vaccine effectiveness was 88.0% 2-9 weeks after dose 2, dropping to 48.5% at 10-14 weeks post dose 2 and dropping further to between 34 and 37% from 15 weeks post dose 2.
Among those who received ChAdOx1 as the primary course, from 2 weeks after a BNT162b2 booster dose, vaccine effectiveness increased to 71.4%. Vaccine effectiveness increased to 75.5% after the booster among those who had received BNT162b2 as the primary course.
With the Delta variant, effectiveness drops from 76.2% 2-9 weeks after dose 2 down to 41.8% at 25+ weeks after dose 2 with a ChAdOx1 primary course. Effectiveness increases to 93.8% 2 weeks after a BNT162b2 booster. With a BNT162b2 primary course, effectiveness drops from 88.2% 2-9 weeks after dose 2 down to 63.5% 25+ weeks after dose 2, increasing to 92.6% 2 weeks after the booster.
UPDATE, 10th December 2021:
“The analysis looked at 581 people with confirmed Omicron. It showed that the AstraZeneca and Pfizer-BioNTech vaccines provided much lower levels of protection against symptomatic infection compared to the protection that they provide against Delta. However, the preliminary data showed effectiveness against the new variant appears to increase considerably in the early period after a booster dose, providing around 70% to 75% protection against symptomatic infection.
16th March 2020:
UK Health Secretary insists ‘herd immunity’ is not part of #coronavirus battle plan.
— Corona Heads Up (@CoronaHeadsUp) March 16, 2020