THE AstraZeneca Covid-19 vaccine (ChAdOx1-S [Recombinant]) was effective at preventing Covid-19 infections due to Omicron when used as a fourth dose booster, according to new data from Thailand's Chiang Mai University.

In the real-word evidence study, AstraZeneca showed vaccine effectiveness (VE) of 73 percent (95 percent confidence interval [CI] 48 percent to 89 percent) against the highly transmissible Omicron variant when a fourth dose was given on top of any previous primary or booster vaccine. According to the study authors, these were the first known data assessing the effectiveness of a mixed (heterologous) four-dose Covid-19 vaccine schedule.