The novel coronavirus, SARS-CoV-2, is an easily spread respiratory virus and the cause of the COVID-19 pandemic. As countries around the world are rolling out the COVID-19 vaccines to control the outbreak, new variants of the COVID-19 virus are threatening these efforts. What makes a virus variant, how does it affect the disease, and will COVID-19 vaccines protect against variants? Here’s what is known so far.
Virus mutations are normal and expected as the COVID-19 virus gets passed person to person. Another name for a mutation is a variation, so mutated viruses are variants of the original virus. (You may see the term virus “strain” used interchangeably with variant and mutant.) Some mutations help the virus, such as making it more contagious. Variant viruses with these types of mutations will usually persist or even overtake the original virus in circulation. This is happening with the new U.K. COVID-19 variant and other variants.
The U.K. variant is named SARS-CoV-2 VOC 202012/01, for ‘Variant of Concern, year 2020, month 12, variant 01.’ Another name for it is B.1.1.7. This virus has many mutations, some of which change or delete parts of the spike (S) protein—the protein required for the coronavirus to infect cells. This protein is the target of many COVID-19 vaccines.
Other COVID-19 variants of concern (VOCs) that are currently causing infections in the United States include one first discovered in South Africa (variant B.1.351), one from Brazil (variant P.1), and two from the U.S. (B.1.427 and B.1.429).
SARS-CoV-2 variant B.1.1.7 is more contagious than the original virus (sometimes referred to as strain G)—spreading 30 to 50% faster, by some accounts. B.1.1.7 quickly became the most common cause of COVID-19 in the U.K. and represents about 60% of all new infections in the U.S. How does that happen? Compared to the original novel coronavirus, the variant virus binds more easily to human cells, accelerating its ability to multiply and cause illness. Coronavirus scientists expect this type of behavior based on the specific changes in the variant. The U.S. and South Africa variants also appear to spread faster than the COVID-19 virus that began the pandemic.
Because viruses like SARS-CoV-2 mutate easily, more variants are likely. Most SARS-CoV-2 mutations are not significant and do not reach the status of “variant of concern.” However, some variants may out-compete the circulating virus strain and become the predominant strain. Check the CDC for more information about these and other variants.
The U.K. variant (B.1.1.7) is more likely than the original circulating virus to cause severe COVID-19 and death. Even if a COVID-19 variant does not cause more severe disease, the problem is more cases of COVID-19 translates to more people potentially needing medical care in a system that is already stretched thin from the existing rate of infection and people needing intensive care.
Researchers are optimistic about vaccine effectiveness against the variants because of how vaccines work. The spike protein would have to change drastically for the virus to evade the immune system in a vaccinated individual (or in someone with natural immunity due to previous infection), and this is not likely to happen.
Still, several variants have certain changes that seem to allow it to evade the immune system, which could render the spike protein vaccines less effective. Laboratory studies with the Pfizer and Moderna COVID-19 vaccines show that antibodies from vaccinated individuals can recognize and neutralize variant viruses, preventing the viruses from multiplying. Neutralization of the mutated virus is reduced compared to the more common circulating virus, but vaccine experts say it is high enough to be protective in a vaccinated individual exposed to a variant.
The B.1.1.7 mutations had a "minimal impact" on neutralization. Indeed, the authorized COVID-19 vaccines are effective against the U.K. variant.
To be proactive, Moderna and Pfizer-BioNTech are testing third shot of vaccine as a booster to determine if it can protect against VOCs in general. In addition, both companies are developing vaccines that could be used as a booster shot to protect against specific variants.
Novavax, which has a COVID-19 vaccine in clinical trials, has early evidence the vaccine is 85% effective against the U.K. variant, but about 50% effective against the South Africa variant.
The Brazil variant (P.1) is troubling because it also may be able to evade the immune system. More studies are underway to understand vaccine effectiveness against P.1.
Reinfection means infection in a person who already had COVID-19, and presumably had at least some natural immunity. There have been reports of reinfection with the variants, but doctors do not yet know the frequency of reinfection. Because the South Africa and Brazil variants appear to evade the immune system to some degree (ability to infect someone who had COVID-19 before and probably had antibodies against the virus), scientists believe reinfection is more likely with these variants than with the more common circulating strain (strain G) in which reinfection is rare.
COVID-19 experts monitor possible reinfection cases closely. They are also tracking COVID-19 cases in people who were vaccinated. There is no evidence so far that the Moderna and Pfizer-BioNTech COVID-19 vaccines do not protect against variants.
The most common diagnostic COVID-19 tests confirm an active infection, but they don’t identify the specific virus variant. If your doctor or the lab that processed your sample needs to know if your infection was caused by a variant, they must perform an additional step: They analyze the sequence of the virus genetic material for mutations. Genetic analysis is not standard practice during testing. However, the U.S. Centers for Disease Control and Prevention (CDC) is analyzing thousands of samples a week to track the spread of variants and identify outbreaks.
Antibody therapies for treating COVID-19 are available. Both therapies are monoclonal antibodies that target a specific part of the spike protein. The antibodies should still target the spike protein of the U.K. variant and reduce the risk of severe illness. However, based on laboratory studies, it’s possible other strains of the COVID-19 virus will limit how well current (and new) treatments work. Drug companies are already adapting existing treatments to target new COVID-19 variants.
Most rapid tests detect a SARS-CoV-2 antigen unrelated to the spike protein, so these tests would detect the new U.K. variant (with its multiple changes in the S protein) in a nasal swab of an infected person. Rapid antigen tests work well as a diagnostic tool when a person has a lot of virus in their nasal swab. But a variant that can infect people more easily and at a lower viral load—perhaps below the level of detection of an antigen test—increases the risk of a false negative result.
There has always been skepticism about using rapid antigen tests due to the risk of false negative results in infected asymptomatic people. New variants that can spread easily without a high viral load in the nose may make antigen tests an even riskier choice over molecular tests like PCR for diagnosing or ruling out COVID-19.