There are over 20 known variants of SARS-CoV-2, the virus that causes COVID-19. Many of these have been of little significance to people who are not epidemiologists. 11 of them have received labels (Greek letters) from the World Health Organization (WHO). Only 5 have been labeled as “Variants of Concern (VOC) ” by the WHO. Of those 5, only 2 remain on the U.S. CDC list for variants of concern, Delta and Omicron.
Omicron, the latest variant, has been widely publicized. It was first sequenced in the country of South Africa, where it has become the only variant currently in circulation.
One of the reasons for alarm was the rapid growth of Omicron cases compared with prior variants. As can be seen in the graph above from Covariants.Org , Omicron became the dominant variant within 2 weeks of detection, and became almost the exclusive cause of COVID infections within 1 month. In comparison, Delta took almost 4 months to become the dominant strain in South Africa.
There are numerous reasons why a variant can become the dominant strain. Human behavior is certainly one of them. Conditions can be favorable at specific times of the year, for example when people in the northern part of the U.S. begin to spend more time indoors due to cold weather. In addition, relaxation of public health measure can also contribute to spread. Also, vaccination rates play a large role in the spread of viruses. At the time of this writing, South Africa has approximately 25% of the population fully vaccinated and 5% partially vaccinated. For comparison, the U.S. currently sits at 60% fully vaccinated and 11% partially vaccinated. However, taking South Africa as a single country study, the omicron variant has certainly spread faster than delta, despite the increase in vaccinations. Lastly, testing makes a difference as well. The number of tests available and the ability to sequence samples to determine the specific variant, has improved over time in South Africa. Despite these factors, omicron is still believed to be more contagious than the delta variant, which we know was already more contagious than prior variants.
Since it’s discovery in South Africa, the NY Times reports that the omicron variant has been detected in 60 countries and the list is growing. The U.S. has detected it in 22 states. This number will undoubtedly continue to grow.
Though the detection and spread of the variant are of concern, there are more important questions that still need answers:
- Does the variant cause more severe illness than delta ? The exact answer is still unknown. But, preliminary data from South Africa does not show an overwhelming surge of hospitalizations coinciding with the surge in omicron cases. That is very good and welcome news, even if it is still preliminary.
- Do the currently available vaccines protect against the omicron variant? Some preliminary data from South African and German studies suggest that vaccine effectiveness against any illness, is lowered with omicron. However, effectiveness against severe disease and death is thought to still be high. And, the effects of a third dose or booster seem to to help restore immunity to levels seen against previous variants. In fact, Professor Alex Sigal, who led the South African study, was quoted as saying “This was better than I expected of Omicron…The virus is so changed, there was concern that it uses a different receptor, not ACE2. If that were the case, many of our pharmacological tools to control this virus would become useless. But this is not the case. Instead, previous infection, followed by vaccination – or likely a booster – is probably protective against Omicron, and almost certainly against severe disease. “
- Do current treatments work against omicron? Regeneron notes its antibody medication, regen-coV “may” be less effective, but more study is necessary. GSK announced its antibody drug sotrovimab was effective against omicron. Merk and Pfizer both report their oral tablets are still effective. Both of those oral therapies target locations other than the spike protein, where the majority of the mutations occurred in omicron. So, yes, our current therapies are thought to be effective against omicron, but more study is necessary.