Study: Booster omicron protection wanes within 10 weeks

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Immunity offered by vaccines wanes more quickly with omicron, finds UK study

The protection conferred by booster vaccines against the omicron variant begins to wane within 10 weeks, according to a briefing released by the UK Health Security Agency (UKHSA).

Based on an analysis of 147,597 delta and 68,489 omicron cases, the agency found that the Oxford/AstraZeneca, Pfizer/BioNTech and Moderna vaccines are less effective against omicron than delta. For people who had two initial doses of the Oxford/AstraZeneca vaccine, the UKHSA estimates that Pfizer/BioNTech or Moderna boosters are around 60 per cent effective at preventing symptomatic infections from omicron 2 to 4 weeks after the third dose, but this falls to 35 to 45 per cent by 10 weeks. For those who had two initial doses of Pfizer/BioNTech, protection falls from 70 per cent at 2 to 4 weeks to 45 per cent at 10 weeks after a Pfizer booster, but stays around 70 to 75 per cent up to 9 weeks after a Moderna booster.

The UKHSA report also estimates that someone infected with omicron is 50 to 70 per cent less likely to be admitted to hospital, compared with delta. This is based on a preliminary analysis of 114,144 omicron cases and 461,772 delta cases occurring between 22 November and 19 December. The difference is somewhat larger than suggested by a study published by Imperial College London on Wednesday, which reported a 15 to 20 per cent lower risk.