How effective are Pfizer, AstraZeneca against Omicron?
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A UK preliminary study shows reduced effectiveness of Pfizer and AstraZeneca vaccines against the Omicron COVID-19 variant.
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WHO noted that the UK study's preliminary results should be interpreted with caution.
The World Health Organization (WHO) confirmed Friday that preliminary results of a UK non-peer-reviewed study showed that the Pfizer and AstraZeneca vaccines are less effective against the Omicron variant than they were against the Delta variant.
Referring to a preprint named "Effectiveness of COVID-19 vaccines against the Omicron (B.1.1.529) variant of concern," during its technical brief on Omicron, the WHO indicated "a significant reduction in vaccine effectiveness against symptomatic disease for Omicron compared to Delta after two vaccine doses of either Pfizer BioNTech-Comirnaty or AstraZeneca-Vaxzevria vaccines."
However, the WHO document read that a Pfizer booster showed higher effectiveness against Omicron two weeks after receiving the shot, which is was slightly lower or comparable against the Delta variant.
The organization noted that these preliminary results should be interpreted with caution.
In November, the WHO identified the new strain as one of concern, as its high number of mutations possibly allows it to proliferate 70 times faster than the original COVID-19 and Delta variants.
