Most COVID-19 vaccines have proven less effective against neutralizing the Omicron variant,, but they still prevent severe illness and death. Third doses of the Pfizer or Moderna vaccines also provide significantly increased protection against the variant.

All viruses naturally evolve over time, developing into new strains, or “variants,” which are then labeled depending on the number of mutations it has and scientists’ predictions on its behavior.

As of December 5, 2021, there is no credible information on the increased severity of the Omicron variant. Researchers and the World Health Organization (WHO) are conducting further testing to better understand the variant.