Key takeaways:
Mutations in the SARS-CoV-2 virus have led to several different variants.
Currently, the Omicron variant is the predominant strain in the U.S., and health officials continue to closely monitor for the emergence of other variants.
Variants are concerning because they could eventually make vaccines or treatments less effective.
When the COVID-19 pandemic began, we all knew the virus by one name: SARS-CoV-2. But over time, this virus started mutating, producing different circulating strains.
Mutations are expected with a long-standing, circulating virus. Some mutations die out, while others allow the virus to adapt and improve its survival. This is concerning because these mutations give the virus an advantage – it could potentially evade an immune response or treatment.
As such, viral variants are classified based on their level of threat to the population. The categories, according to the Centers for Disease Control and Prevention (CDC), are as follows:
A variant being monitored provides a low level of threat but is still on the radar.
A variant of interest has genetic sequence changes that could cause increased spread, more severe disease, or the ability to evade treatment or vaccination.
A variant of concern has shown the ability to increase transmission, cause more severe disease, or evade treatment or vaccination.
A variant of high consequence is one that makes treatment and vaccines less effective, affects more vaccinated people, and causes more severe disease and hospitalizations on a “significant” scale.
There are currently no variants of high consequence. Also note that the CDC’s list of variants is different from that of the World Health Organization (WHO). This is because the CDC is monitoring variants in the U.S., while the WHO tracks variants’ effects across the globe.
So far, these have been the variants of concern in the U.S.:
Alpha (December 29, 2020 – September 21, 2021)
Beta (December 29, 2020 – September 21, 2021)
Delta (June 15, 2021 – April 14, 2022)
Epsilon (March 19, 2021 – June 29, 2021)
Gamma (December 29, 2020 – September 21, 2021)
Omicron (November 30, 2021 - current)
Check back here for future updates on COVID-19 variants.
Latest Omicron subvariant ‘most transmissible’ yet
January 6, 2023
At the start of this new year, health officials in the U.S. are closely watching a new Omicron subvariant called “XBB.1.5.” It currently accounts for about 27% of infections in the U.S. and is on pace to edge out subvariants BQ.1 and BQ1.1. Notably, XBB.1.5 has already become the predominant strain in the Northeast, where COVID-related hospitalizations of older adults are increasing.
Data suggest XBB.1.5 is more highly transmissible than previous Omicron subvariants. But it’s too early to say if it will cause more severe illness. Experts say that bivalent booster vaccines and COVID prevention actions are still the best way to stay protected.
Omicron subvariants BQ.1 and BQ1.1 gaining ground in U.S.
November 23, 2022
The U.S. is again facing new Omicron subvariants that are increasingly better at evading immunity. The newest subvariants — BQ.1 and BQ1.1 — appear to be much more immune-evasive than previous ones. They currently account for over half of U.S. COVID cases, outpacing the previous dominant subvariants BA.4 and BA.5.
Experts encourage everyone who is eligible to receive updated booster shots, which target Omicron, unlike the original boosters. They also urge caution for people who are immunocompromised, especially because some treatments will likely not be effective against BQ.1 and BQ1.1. The number of hospitalizations due to COVID is currently stable, but the rise in hospitalizations due to other respiratory viruses is causing concern among public health officials.
Newest Omicron subvariants BA.4 and BA.5 on pace to outcompete original
June 23, 2022
Public health experts are closely monitoring new Omicron subvariants as hospitalizations due to COVID-19 continue to rise.
Omicron subvariant BA.2.12.1, which evolved from BA.2, was first identified in the U.S. in March and is now the predominant subvariant here. But newer Omicron subvariants BA.4 and BA.5 are rapidly gaining traction. All are more contagious than the original Omicron variant. However, it’s too early to tell if BA.4 and BA.5 will cause more severe illness.
BA.4 and BA.5 have been circulating in Africa and Europe since early this year, but only recently were detected in the U.S. At the end of May, they accounted for less than 10% of cases in the U.S. They currently account for about one-third of cases, showing rapid spread.
Boosters appear to be less effective against BA.4 and BA.5 than against BA.2. What’s more, research suggests that immunity from an earlier infection with Omicron subvariant BA.1 may not protect against infection with BA.4 or BA.5. In other words, people who had an earlier Omicron infection are at risk for reinfection, especially if they’re not vaccinated and boosted.
The FDA’s vaccine advisory committee will meet later this month to discuss whether to modify vaccines for variants. They need to plan now to allow enough time for vaccine development and distribution. But it’s hard to predict which variant or subvariant will be circulating by the time a new vaccine is ready.
COVID-19 cases increasing in the Northeast due to BA.2 variant
April 12, 2022
Public health officials are carefully watching an uptick in COVID-19 cases in the U.S. — primarily in the Northeast — driven by Omicron subvariant BA.2.
BA.2 currently accounts for 72.2% of cases in the U.S. and is responsible for closer to 84% of cases in northeastern states. But due to milder symptoms, more at-home testing, and less public testing, officials believe cases are likely underreported. Hospitalizations and deaths remain low, but these numbers typically lag behind increases in cases.
Numbers in the U.S. also typically follow those of European countries and the U.K., which both recently saw a spike in cases. That spike was accompanied by a small rise in hospitalizations, but not deaths.
Meanwhile, experts are also watching Omicron XE. It is a recombinant subvariant, meaning it has genetic material from multiple variants — in this case BA.1 and BA.2 subvariants. XE has been identified in the U.K. and a few other countries, including the U.S. Data on XE are limited due to the small number of cases.
Experts maintain that the best means of protection against COVID-19 infection or reinfection is to get vaccinated, including boosters for those who are eligible.
‘Stealth Omicron’ subvariant on the rise in the U.S.
March 21, 2022
Many places in the U.S. are relaxing anti-COVID measures, and COVID-19 cases are falling. But experts warn of an increase in cases due to the rise of the Omicron subvariant BA.2, also known as “stealth Omicron.”
COVID-19 cases are increasing in the U.K., driven by an increase in BA.2, and trends in the U.S. typically follow suit. BA.2 currently accounts for approximately 23% of cases in the U.S., up from 0.8% at the end of January.
The World Health Organization has said that BA.2 is more transmissible than the original Omicron (BA.1). But so far it does not appear to cause more severe illness. Early data suggest that mRNA vaccines offer similar protection against BA.1 and BA.2. Public health officials are continuing to monitor the situation but don’t expect a significant increase in hospitalizations.
Omicron subvariant in the spotlight
January 28, 2022
A subvariant of the Omicron variant, called “BA.2,” is making headlines. It’s not a separate variant but more like a “sibling” of the Omicron variant. BA.2 was originally identified in November (at the same time as Omicron) in South Africa, but it has only recently begun to make headlines.
So far, authorities have detected BA.2 in 54 countries, including the U.S. It’s the dominant strain in India and accounts for approximately 50% of cases in Denmark. It doesn’t appear to cause more serious illness than Omicron, but it could be slightly more contagious. Data from the U.K. suggest that the effectiveness of the vaccine booster against BA.2 is similar to that of Omicron.
How Omicron differs from previous variants
January 4, 2022
Record numbers of COVID-19 cases are being recorded in the U.S. and around the world due to the Omicron variant. But while Omicron maintains its status as the dominant variant in the U.S., recent data highlight significant differences between it and the Delta variant.
First, Omicron continues to be more infectious, with a much more rapid spread. And it may have a shorter incubation period. There is also growing evidence that it causes symptoms more like the common cold versus loss of taste and smell and the possibility of pneumonia seen with previous variants. Finally, U.K. studies suggest that infection with Omicron is associated with a lower individual risk of hospitalization.
While this may all sound like good news, there is still cause for concern. The sheer number of cases is overwhelming healthcare workers and systems in many areas around the country. Also, data suggest the available vaccines may be less effective against Omicron than Delta.
Fortunately, booster vaccine doses improve protection against hospitalization. Both vaccines and previous infection result in immunity from a combination of antibodies and T-cells, although vaccination elicits a stronger response. And even though Omicron may be able to get around antibody-based immunity, recent data (not yet peer-reviewed) suggest it is still susceptible to T-cell immune response.
Omicron overtakes Delta in US
December 21, 2021
Omicron is now officially the dominant COVID-19 variant in the U.S. According to the CDC, Omicron accounts for 73% of cases, after having first been identified here on December 1. The spread of this variant is much more rapid than previous ones, surprising even some experts.
Data from the U.K. (not yet peer-reviewed) suggest Omicron does not lead to less severe cases, as previously hoped. Additionally, projections from Denmark — a country with high rates of testing and vaccination — suggest further increases in cases and hospitalizations are likely to occur. Vaccine boosters from Pfizer and Moderna may be able to slow the spread, so experts urge everyone who is eligible to get their booster shot for as much protection as possible. To date, only 30% of Americans have received a booster.
Omicron continues rapid spread
December 10, 2021
In a press conference on December 8, WHO representatives addressed ongoing global concern about the Omicron variant. It has been identified in at least 57 countries, and that number is expected to grow. So far, it seems this variant makes reinfection more likely for people who have had COVID, but infection may be milder than with Delta. Officials made it clear that more data is needed before drawing firm conclusions.
Omicron “is likely to outcompete Delta” and become the predominant strain in the U.K., where cases are doubling every 2 to 3 days. Omicron has been identified in at least 25 states in the U.S., but Delta remains the dominant variant.
Omicron new ‘variant of concern’
November 29, 2021
The WHO has classified SARS-CoV-2 variant B.1.1.529 – called Omicron – as a variant of concern.
South Africa identified and reported the variant, but it has been found in several areas around the world, including European countries, Canada, Australia, and Hong Kong. This variant is particularly concerning due to the large number of mutations in its spike protein, which affects the virus’s ability to infect human cells.
That said, it’s too early to tell if Omicron is more contagious or causes more severe disease. There is no evidence to suggest it causes different symptoms, but it may make it easier for those who have already had COVID to get it again. Expect more information on this, as well as vaccine efficacy against Omicron, in the coming days and weeks.
Currently, experts recommend the usual precautions against virus transmission: wearing a mask, avoiding crowded spaces, social distancing, and getting the vaccine (or booster). However, vaccination rates and availability are uneven around the globe. This is important because variants are more likely to occur among populations with less protection. Increasing vaccine availability will be important moving forward to reduce the likelihood of more variants developing.
‘Delta plus’ may be more contagious than original Delta variant
October 27, 2021
A subtype of the Delta variant, AY.4.2, has made its way to the U.S. Also called “Delta plus,” the subtype is currently responsible for approximately 10% of cases in the U.K. There is concern that it could be more contagious than the Delta variant that created the most recent wave here. But there is more to learn. Regardless, it is a good reminder of SARS-CoV-2’s ability to mutate.
It’s too early to tell how AY.4.2 will affect us, if at all. Authorities continue to monitor this and other subtypes of the Delta variant.
Delta now outpacing other variants worldwide ‘by far’
September 22, 2021
The Delta variant is “by far” the most dominant worldwide, according to a recent WHO video Q&A. As it spreads, it is replacing other variants: Alpha, Beta, and Gamma currently represent only 1% of sequences studied. The most transmissible variant, Delta has been found in 185 countries. It is thought to be responsible for up to 98% of COVID-19 cases in the U.S.
Mu variant added to WHO list of variants of interest
August 30, 2021
The WHO has added the Mu variant to its list of variants of interest. This variant originated in Columbia in January and has since spread throughout Columbia and Ecuador. It has also been reported in the U.S., Spain, and Mexico. Concern about the potential for vaccine resistance prompted the listing by the WHO.
Delta variant becomes dominant COVID strain in the US
July 7, 2021
The Delta variant has become the most dominant variant in the U.S., causing more than 50% of COVID-19 cases. It replicates faster, allowing it to spread more quickly. But its symptoms remain the same as previous variants (fever, cough, fatigue, headache, and loss of taste or smell), and experts believe the available vaccines will continue to provide protection.
New COVID variants may evade immunity
June 21, 2021
With coronavirus, the concern is that we’ll eventually see a variant so different from the original virus (for which vaccines were developed) that vaccines no longer work well. Currently, vaccines appear to be similarly effective against variants. However, researchers have found that antibodies that people developed after infection with the original strain may be less effective against new variants.
Delta now variant of concern according to CDC
June 15, 2021
The CDC has upgraded the Delta (B.1.617.2) variant from a variant of interest to a variant of concern. This is consistent with the WHO’s classification and represents the growing threat to the U.S. population. Delta continues to demonstrate rapid spread due to its increased transmissibility.
Additionally, the Lambda variant is now a variant of interest, according to the WHO.
New WHO system for naming COVID variants
May 31, 2021
As time goes on, there are an increasing number of mutations and resulting variants to keep track of. Researchers use an alphanumeric naming system to differentiate between them, but these names have quickly become confusing for the rest of us. Naming variants according to geographic locations may seem easier to some, but doing so can create stigma.
So the World Health Organization (WHO) has announced a new naming system for SARS-CoV-2 variants. The new labels – letters of the Greek alphabet – were chosen because they are simple and easy to remember. They will not replace the scientific names but will make public health communication and reporting easier and less confusing.
Variant B.1.617.2 upgraded by WHO to variant of concern
May 11, 2021
The WHO has reclassified variant B.1.617.2 to a variant of concern. It originated in India and was previously considered a variant of interest. This decision to upgrade was based on the variant’s ability to spread more easily and some evidence that it could make vaccination less effective. As of now, researchers say vaccines are still the best form of protection against COVID-19.
How does the COVID virus mutate?
March 2020
Random genetic mutations in viruses are expected over time. As the virus replicates, errors in the genome occur, and then they get passed on. The mutations that give the virus an advantage tend to thrive and become dominant.
In the case of SARS-CoV-2, mutations in the genetic code for the virus’s spike proteins have been uncovered. These spike proteins are important to how the virus infects other cells. Specifically, researchers recently noted that a variant with a specific spike protein mutation – making the virus more infectious – has become more predominant in Europe. Experts will continue to monitor its effects in the U.S. and across the world.
The bottom line
Why trust our experts?
As long as the global COVID-19 pandemic continues, and the virus is given the chance to mutate, we will continue to see different variants. At this time, vaccination is still the best protection against existing variants.
