WHO designated the variant B.1.1.529 (named Omicron) a variant of concern on 26 November because it has a large number of mutations, some of which are concerning. They are concerning because they can potentially affect virus characteristics such as transmissibility, disease severity, immune escape, diagnostic or therapeutic escape. At the time of assessment, the Omicron variant also appeared to be increasing in almost all provinces in South Africa, and there was some evidence of an increased risk of reinfection with this variant compared to other variants of concern.
More evidence on the variant’s characteristics is being collected, and as of 30 November 2021, it is not clear yet whether Omicron has more potential immune escape, is more transmissible or cause more severe disease than other variants. It is also not yet known whether currently available vaccines will be less effective, to any degree, against this variant.
Vaccines are highly effective in protecting against severe COVID-19 disease and death, including against the currently dominant Delta variant. They also reduce but do not eliminate the risk of infection. Vaccine effectiveness against mild or severe disease may vary, depending on the product and the variant, but vaccines will continue to be the most important first line of defense against this disease, and they are especially important for people who are most at risk, including older adults, health workers and people with underlying health conditions.
The best way to prevent infection and serious disease caused by Omicron or any other SARS-COV-2 variant is by getting vaccinated and remembering to also maintain physical distance, wear a mask when distancing is not possible, frequently wash hands and ventilate indoor spaces.