Booster efficacy against symptomatic Omicron reduces within 10 weeks

A recent study by the United Kingdom Health Security Agency reveals that the efficacy of the Covid booster shot against symptomatic cases of the Omicron variant decreases within a period of ten weeks. "Repeated VE analysis continues to show lower VE for symptomatic Omicron disease compared to Delta. There is evidence of waning of protection against symptomatic disease with increasing time after dose 2, and by 10 weeks after the booster dose, with a 15 to 25% reduction in vaccine effectiveness after 10 weeks," read the report. 

The study analysed 147,597 Delta and 68,489 Omicron cases, reported between November 27 and December 17. 

As a first step, the researchers analysed the percentage of vaccine efficacy in between the two strains. This was with people who had received the two doses of AstraZeneca, Pfizer or Moderna Covid vaccine.

Then, the researchers compared the efficacy rate of the vaccines between the two different variants. 

It was concluded that efficacy against the Omicron variant was lower than that of the Delta variant. However, the report further warned that there are insufficient severe cases of Omicron to analyse vaccine effectiveness against hospitalisation. 

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Several nations across the world are struggling to control the rapid spread of the Omicron variant. While some countries are reimplementing Covid regulations, others are hoping that they will get rid of the new variant by vaccination.

However, scientists are still 'surprised' by the properties of the Omicron variant.

Professor Ravi Gupta, a member of the New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG) told Sky News, that even after almost a month of discovering this new variant, scientists are still learning ‘all the time’ about Omicron and its properties.

"Some experiments that have been done in different groups are suggesting that the virus has kind of altered the way it infects cells,” Gupta said. "This is again potentially due to some mutations that have occurred, and there may, and this is a big caveat, there may be a slightly different profile for this virus [compared to Delta]."

(With inputs from agencies)