Since the Omicron variant began its takeover, the number of people reinfected with the coronavirus has been rising sharply — a trend not observed with previous variants. Scientists are now getting some clues that the surge might be due to Omicron’s unique capacity to evade the body’s immune defenses.
Scientists believe that Omicron’s ability to infect people with either vaccine- or infection-derived immunity plays a vital role in what drove the recent global surge.
Data from South Africa, England, and recently from Qatar all suggest that the immunity acquired through previous infection or vaccination is less effective against the Omicron variant.
In a study based in Qatar, scientists measured the extent to which Omicron could evade immunity. Despite being 90% effective at preventing reinfection with the Alpha, Beta, or Delta variants, the immunity was only 56% effective against Omicron infection. Most reinfections occurred about one year apart, showing that a previous infection offers protection at least for some time. More importantly, the protection against severe COVID-19 caused by Omicron remained high – around 88% – being unable to protect against reinfection.