What you need to know about the coronavirus variants

Updated Sept. 3 at 8:59 a.m.

Viruses are always mutating and taking on new forms, and thousands of variants of the coronavirus have been identified. But several, including variants first found in the United Kingdom, South Africa, Brazil and India, are highly transmissible and have sparked concerns that vaccines may be less effective against them.

The delta variant (B.1.617)

Where and when was it discovered?

This variant was first detected in Maharashtra, India, in October and contributed to a devastating surge in infections in that country this spring.

Where is it now?

The delta variant has been reported in dozens of countries, including the United States, United Kingdom, South Africa, Uganda and Kenya. As of July, delta represented more than half of new infections in the United States.

What makes it different?

Delta appears to be about 50 percent more contagious than the alpha variant, which became the predominant variant in the U.S. in the spring. There is limited data on whether delta results in more severe illness than other variants.

Monica Gandhi, an infectious-diseases expert at the University of California at San Francisco, told The Washington Post that delta is the most “fit” variant, which means it will probably outcompete others to infect more people.

Will vaccines work?

All three vaccines authorized in the U.S. appear to be effective against severe disease and death from delta, but may offer weaker protection against minor to moderate illness. For the two-dose mRNA vaccines, both doses are important for warding off the delta variant.

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The mu variant (B.1.621)

Where and when was it discovered?

This variant was first reported in Colombia in January 2021 and classified as a “variant of interest” by the World Health Organization in late August. Mu is the fifth variant of interest currently being monitored by the WHO.

Where is it?

The mu variant has been identified in more than 39 countries so far, according to the WHO. It remains on the rise in Colombia and Ecuador, the health body said, with other outbreaks reported in nations in South America and Europe. Cases have also been reported in the United States, mostly in California, New York and Florida.

What makes it different?

Preliminary data showed the mu variant shares some similarities with the beta variant, according to the WHO, and like that strain, it appears vaccines may have a diminished impact. There is no evidence, however, that it is more lethal and the WHO has called for further studies. The organization also said that it would monitor how the mu variant may interact with the more common delta variant.

Will vaccines work?

The vaccines may be less effective against the mu variant, but it remains unclear. The WHO has said, “has a constellation of mutations that indicate potential properties of immune escape.” It added that “more studies are required to understand the phenotypic and clinical characteristics of this variant.”

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The lambda variant (C.37)

Where and when was it discovered?

This variant was first identified in Peru in August 2020. It spread rapidly there in 2021 and now accounts for the majority of new cases.

Where is it?

At least 29 countries have reported lambda infections. Chile, Argentina and Ecuador have seen the most significant increases outside of Peru, according to the World Health Organization. It has also been detected in Mexico and throughout Europe, though in relatively smaller numbers.

Lambda has circulated in the United States for months but its progress has been slow, with fewer than 700 cases reported as of July 20. Experts say it is being vastly outcompeted by the delta variant.

What makes it different?

The lambda variant may be more transmissible than the original version of the virus. The WHO designated it a 'variant of interest” in June, meaning scientists have observed genetic changes that could pose increased dangers. The variant has some of the same types of mutations observed in the alpha, beta and gamma variants that may make it more contagious. It also has a mutation similar to one found in delta that may allow it to more easily infect lung cells.

Will vaccines work?

A paper by New York University researchers, posted on July 19, found that the Pfizer and Moderna vaccines had no problem neutralizing lambda. The variant showed a slight resistance to the two mRNA vaccines, but the shots were still highly effective, according to the study, which has not yet undergone peer review. The Johnson & Johnson vaccine was significantly less effective, the researchers found, though it still provides some protection.

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The beta variant (B.1.351)

Where and when was it discovered?

This variant, also referred to as 501Y.V2, was found in South Africa in early October and announced in December, when the country’s health minister said the strain seemed to affect young people more than previous strains. It may have contributed to a surge of infections and hospitalizations across South Africa.

Where is it?

The beta variant has been identified in more than 80 countries. On Jan. 28, South Carolina officials announced that this variant had affected two people there with no travel history — the first instances of this strain identified in the United States. It has since been found in at least three dozen other states.

What makes it different?

This variant shares some similarities with the alpha variant and, like that strain, appears to be more transmissible. There is no evidence that it is more lethal. Former Food and Drug Administration commissioner Scott Gottlieb has suggested that this variant might be more resistant to antibody therapies.

There is some evidence that the beta variant could allow for reinfection: A man in France was in critical condition in mid-February after being infected with this strain four months after he was previously infected with the virus.

Will vaccines work?

The vaccines may have a diminished impact against this variant, but they probably will still be effective, Anthony S. Fauci, the U.S. government’s top infectious-disease expert, said in January. Moderna has said its vaccine protects against the beta variant, with an important caveat: The vaccine-elicited antibodies were also less effective at neutralizing this variant in a laboratory dish.

Pfizer and BioNTech released their own study, not yet peer-reviewed, that suggests that their vaccine effectively neutralizes this variant, though was slightly less effective.

On Jan. 29, Johnson & Johnson said its single-shot vaccine was robustly effective in a massive global trial, but that its protection against sickness was weaker in South Africa. Biotechnology company Novavax has also indicated that its vaccine was significantly less effective during a trial in South Africa.

In South Africa, the distribution of the Oxford-AstraZeneca vaccine was halted. The vaccine did not provide sufficient protection against mild and moderate cases caused by a new variant, health officials said.

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The alpha variant (B.1.1.7)

Where and when was it discovered?

This variant was first found in the United Kingdom, specifically in London and the nearby county of Kent, in September. It is sometimes referred to as the “Kent” variant. It began spreading rapidly in Britain, Denmark and Ireland in December.

Where is it?

Dozens of countries have seen infections from this variant of the virus. The Centers for Disease Control and Prevention announced in April that this variant had become the dominant one in the United States.

What makes it different?

The alpha variant appears more transmissible than the more common strain. This strain also may be 30 to 70 percent more lethal than previous variants.

Will vaccines work?

The scientific consensus is that the vaccines will remain effective against this variant because those inoculations provoke an array of neutralizing antibodies and other immune-system responses. Pfizer, Moderna and Novavax have said their vaccines appear to work against this variant.

Ravindra Gupta, a professor of clinical microbiology at the University of Cambridge, found in a study of older adults that the immune response triggered by the Pfizer vaccine was modestly less effective against the alpha variant.

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The gamma variant (P. 1)

Where and when was it discovered?

Sequencing studies found the variant in Brazil, mainly in Rio de Janeiro, as early as July 2020. Researchers in Japan discovered it in travelers from Brazil in January.

Where is it now?

It has been confirmed in more than two dozen countries, including Japan, Spain and New Zealand. On Jan. 25, Minnesota health officials confirmed the first U.S. case of this variant in a resident with recent travel history to Brazil. It has since been found in more than 30 states.

What makes it different?

The variant has more than a dozen alterations, several of which are found on the virus’s spike protein, which binds the virus to a cell. Because of that, researchers think the strain is probably more transmissible. There is also some evidence that antibodies might not recognize the P.1 variant, which could lead to reinfection.

Will vaccines work?

There’s no strong evidence suggesting vaccines won’t work against the gamma variant. But scientists have raised the possibility that this variant can evade antibodies, which would impact the vaccines’ effectiveness.

A study of the Pfizer vaccine published in March determined that it was highly effective at neutralizing the gamma variant. Moderna has announced that it would develop a new vaccine tailored to a similar variant in case an updated shot becomes necessary.

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The iota variant (B.1.526)

Where and when was it discovered?

This variant, which was found in samples obtained as early as November, probably emerged in the Washington Heights section of New York, Fauci told reporters in March. By the middle of that month, this variant made up nearly half of the city’s new infections.

Where is it now?

Officials have reported this variant in at least 14 other states, including Texas, Wyoming and Maryland, Bloomberg reported.

What makes it different?

Some scientists are concerned that this variant may be more transmissible than previous versions. Gottlieb expressed worry that a mutation on this variant could enable it to reinfect people who have already had the virus.

Will vaccines work?

This variant seems to have some resistance to existing vaccines, although not as much as the beta variant, Fauci said on CBS News’s “Face the Nation.” Gottlieb said he was also concerned that this variant could partly elude the effects of vaccination.

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The ‘Eeek’ mutation (E484K)

Where and when was it discovered?

This might best be described as a mutation within a variant. It’s called E484K — or “Eeek,” as epidemiologists refer to it — and it’s appearing on some of the variants we describe below. It’s not brand new; it has appeared many times since the start of the pandemic, but experts have been concerned about it. It gained mainstream attention when it started to coincide with other variants that are more contagious.

Where is it?

Eeek has been seen in the beta and gamma variants and some strains of the alpha variant.

What makes it different?

The Eeek mutation changes the virus’s spike protein, which is what vaccines target. By itself, this mutation does not change the virus significantly. This mutation is concerning when paired with the variants — a combination that could help the virus evade detection and make neutralization by the human immune system less efficient.

Will vaccines work?

Scientists are actively trying to answer this question. Clinical trial data have indicated that vaccines were less effective in preventing infections with variants in South Africa featuring the mutation. But the vaccines still dramatically lowered the chance of severe illness or death.

Semi-related to the vaccine question: One study found preliminary evidence that patients in South Africa who had survived an earlier bout with the more common coronavirus were becoming infected a second time — though were not made severely ill — after exposure to the variant with this mutation.

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The Denmark/California mutation (L452R)

Where and when was it discovered?

This mutation was detected in Denmark in March 2020.

Where is it now?

A variant with this mutation was found in California last winter and became dominant there over five months, eventually making up more than half of infections in 44 of the state’s 58 counties. This mutation has also been confirmed in several other states.

What makes it different?

There is evidence that this mutation enhances the virus’s ability to bind to human receptor cells, making it more transmissible. Some scientists have urged public health officials to declare the variant with this mutation circulating in California a “variant of concern,” which would make it the first homegrown variant with this label.

Will vaccines work?

Some scientists think this mutation might make the virus more resistant to vaccines because the mutation is in the spike protein, which enables the virus to attach to cells. But scientists also say that more study is needed before they can draw conclusions.

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The original variant (D614G)

Where and when was it discovered?

This variant, known to scientists simply as “G,” was discovered in China in January 2020. It soon spread through New York City and Europe.

Where is it?

The “G” variant has become ubiquitous. By July 2020, about 70 percent of the 50,000 genomes of the coronavirus uploaded by researchers worldwide to a shared database carried the variant.

What makes it different?

Some scientists think this variant is significantly more transmissible than the original strain of the virus. That’s because this variant has four to five times more spikes on its surface. Those spikes enable the virus to latch onto and infect cells. But other scientists still contest the greater transmissibility.

Will vaccines work?

The G variant was the dominant strain when 2020 vaccine trials took place. The Pfizer and Moderna vaccines showed a 95 percent efficacy in trials. The Johnson & Johnson vaccine, which faced both the G variant and the beta variant, was found to be 66 percent effective at preventing moderate or worse cases of the virus.

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What do the variants mean for vaccines?

“We need to get as many people vaccinated with the current vaccine that we have as we possibly can … and prepare for the potential eventuality that we might have to update this vaccine sometime in the future.” — Fauci in January

As more significant variants are reported, the obvious (and arguably most important) question is whether the vaccines will work on them. Some of the mutations have sparked particular concern because they affect the spikes on the virus, which is what the vaccines target.

In short, the pharmaceutical companies are testing new variants against their vaccines and spinning up new trials. Moderna and Pfizer can update their vaccines quickly because of their mRNA technology, which can be reprogrammed to target new variants.

A growing number of scientists anticipate that we will eventually need something similar to the annual flu shot — companies will periodically update their vaccines to match the prevalent coronavirus variants, and we will need to get boosters to stay protected.

“With flu, we need to adapt the vaccines. We can see that already,” said Ravindra Gupta, a professor of clinical microbiology at the University of Cambridge. “The companies do realize there is a problem in the longer term, and they will deal with it just as we have done with flu every year.”

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Joel Achenbach, Lindsey Bever, William Booth, Carolyn Y. Johnson, Sarah Kaplan, Laurie McGinley and Fenit Nirappil contributed to this report.

Marisa Iati is a reporter for the General Assignment News Desk at The Washington Post. She previously worked at the Star-Ledger and NJ.com in New Jersey, where she covered municipal mayhem, community issues, education and crime.
Angela Fritz is the Deputy Editor on the General Assignment News Desk. She is also an atmospheric scientist and was formerly Deputy Weather Editor on the Capital Weather Gang. Before joining The Post, Fritz worked at CNN in Atlanta and Weather Underground in San Francisco. She has a B.S. in meteorology and an M.S. in earth and atmospheric science.
Derek Hawkins is a reporter covering national and breaking news. He previously covered cybersecurity for PowerPost and wrote about law, crime and politics for The Washington Post's Morning Mix.
Adela Suliman is a breaking-news reporter in The Washington Post's London hub.