LONDON (BLOOMBERG) - A previous Covid-19 recovery provides little shield against infection with the Omicron variant, a research team from Imperial College London showed in a large study that underlines the importance of booster shots.
Having had Covid probably only offers 19 per cent protection against Omicron, the study showed on Friday (Dec 17). That was roughly in line with two doses of vaccine, which the team estimated were as much as 20 per cent effective against Omicron.
Adding a booster dose helped dramatically, blocking an estimated 55 per cent to 80 per cent of symptomatic cases.
The Imperial College London team analysed all the PCR test-confirmed Covid cases in England between Nov 29 and Dec 11, making it one of the most expansive examinations yet of Omicron's potential to evade the body's defences.
The results were in line with the picture emerging of the variant's capacity to elude protection from previous infection or inoculation and spread faster than previous iterations of the virus.
There was no evidence of Omicron cases being less severe than Delta, based on the proportion of people testing positive who had symptoms or went to the hospital, the team said. Just how severe Omicron cases will be remains unclear. It's too soon to say how hospitalisations will play out in the UK.
In South Africa, which announced the discovery of the variant on Nov 25, authorities said on Friday the rate of hospitalisations seems to be lower than during the country's earlier wave of Delta infections.
Europe is bracing for an Omicron-driven fifth wave of infections even as intensive-care units in many areas remain filled with patients sick with the Delta variant.
Some governments are already imposing new measures in an effort to slow the Omicron wave and buy time for booster campaigns to gear up.
The proportion of Omicron among all Covid cases was probably doubling every two days up to Dec 11, the UK team said, estimating that every person infected with the variant passed it on to more than three other people.