Scientists from the University of Toronto found that those who contracted COVID during the first wave in 2020 were 40% less likely to be reinfected in the first six months of Omicron’s operations than those without the coronavirus. The study will be presented at the European Congress of Clinical Microbiology and Infectious Diseases (ECCMID 2023).
Scientists analyzed the data of 618 patients who recovered from coronavirus in the first wave of the pandemic (March-September 2020), and 168 people who were not infected during this period. The mean age was 56-57 in both groups.
Compared with adults who did not have COVID-19 during the first wave, adults who recovered from the first wave were 40% less likely to become infected during the first six months of omicron variant activity (December 2021 to May 2022).
Individuals aged 65 years and older were 66% less likely to be infected with the omicron variant, and the risk was not dependent on whether or not they were sick in the first wave.
In addition, vaccination, as expected, provided significant protection as well as innate immunity and reduced the risk of infection by 24-65% during the micron wave.