Vaccines also reduce the risk of developing severe disease or being hospitalized with omicron. However, with a booster shot, the vaccine effectiveness rose to 67%, and then fell to about 45% after about 10 weeks, the researchers found. A study published in March in The New England Journal of Medicine found that the vaccine effectiveness of two doses of the Pfizer vaccine was 65%, but this fell to about 9% more than 25 weeks after vaccination. Because of the high number of mutations that omicron has on its spike protein, scientists expected that vaccines would be less effective against omicron compared with previous variants.Īnd indeed, there has been an increased number of breakthrough infections with omicron compared with earlier variants. And BA.2 is more contagious still - it's estimated to be 1.5 times more transmissible than BA.1, CNBC reported.ĭo vaccines work? Most COVID-19 vaccines, including those used in the U.S., prime the immune system against the spike protein, Live Science previously reported. Some studies estimate that omicron's BA.1 variant is 4 times more transmissible than the delta variant, according to CNBC. Why is the variant concerning? The omicron variant has a very high number of mutations in the spike protein that appear to make it more transmissible and allow it to at least partially evade vaccines. For example, omicron has the N501Y mutation, which is also found in the alpha variant, and is thought to make the virus more contagious, according to The New York Times. Some of omicron's other mutations have also shown up in previous variants of concern.
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What are key mutations? Omicron has more than 30 mutations in the genes that code for its spike protein, with 10 of those genes coding for parts of the "receptor binding domain," or the part of the spike protein that latches onto human cells, Live Science previously reported. Between March 6 and March 12, BA.2 accounted for an estimated 23.1% of new coronavirus cases in the country, Live Science previously reported. BA.1 was primarily responsible for the winter surge in COVID-19 cases, but cases of BA.2 have since increased dramatically in Europe and are beginning to rise in the U.S.
As of mid-March 2022, omicron is the dominant coronavirus variant in the world, accounting for 99.9% of coronavirus genome sequences from recent COVID-19 cases in the global database GISAID, according to WHO.Īt the beginning of December 2021, researchers spotted another version of omicron, and proposed splitting the omicron lineage into two sublineages: BA.1, the version initially found in Africa, and BA.2, for the newfound version.
Where is it now? Omicron quickly spread around the world, causing a surge of COVID-19 cases in December 2021 and January 2022.
As such, the alpha, beta and gamma variants were designated as "previously circling VOCs," and delta and omicron were designated as "currently circling VOCs." In addition, the VOIs named lambda and mu were designated as "previously circulating VOIs, according to WHO. And in March 2022, WHO officials said that variants would be further designed as "currently circulating" or "previously circulating," according to the WHO report. For example, the variants named eta, iota and kappa were once considered VOIs, but that label has since been removed and those variants are no longer being monitored, according to WHO. Officials use the term "variant of concern," or VOC, once reliable data show that the variant has increased transmissibility - such as what's been seen with the omicron variant - or other worrisome features, such as the ability to evade vaccines or cause more severe disease, as was the case with delta, Live Science previously reported.īut the VOI or VOC labels can be removed if evidence shows that a variant no longer poses a major risk to public health compared with other variants, or they aren't circulating at significant levels, according to WHO.
In particular, a "variant of interest," according to WHO, is a variant that is increasing in prevalence in multiple areas and has mutations that are likely to affect viral characteristics, such as transmissibility or disease severity. Viruses mutate all the time, so these new variations have not been surprising however, when a modified version becomes a dominant strain in a region or one with worrisome features, public health experts name and follow those versions.
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