VE against infection by Omicron was lower than for previous variants and waned over time with most protection against infection lost by 4-6 months post second dose.
#Omicron series#
For considerations on these doses, see Ī systematic review of the evidence published between December 2021 and April 2022 in The Lancet Infectious Diseases found that the VE of a primary series (for most people, this is two doses) against severe outcomes remained high and stable over time at over 80%. Fourth doses, or second boosters, are most important for those at high risk of severe outcomes.Immunity against infection wanes over time, but can be boosted with a third or fourth dose of an mRNA vaccine. COVID vaccines are not always able to provide protection against infection by Omicron or one of its subvariants.A booster dose is recommended at 5 months after the second dose, and at least 3 months following infection with COVID-19, to increase the level of protection against severe outcomes. Two doses of a COVID vaccine dramatically reduce the risk of hospitalization or death, and a third dose will offer even more protection.
The protection that vaccines provide against severe disease continues to be strong even many months after immunization.This occurs whether this immunity was generated by infection, vaccines, or both. Omicron has demonstrated increased transmissibility and capacity to evade the body’s immune response compared to previous versions of the virus.Omicron, along with its sub-variants, is the currently circulating variant of concern (VOC) in Alberta. These changes can cause the emergence of new “variants” of the original virus and may have different properties than the original virus, such as increased transmissibility or the ability to cause more severe disease. All viruses evolve over time through genetic variations.A large body of evidence suggests that vaccines are safe and effective against COVID-19.
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