EXPLAINER

A vaccinated person's guide to the most concerning COVID-19 strains

Are all the vaccines equally effective against the variants of concern? We dug into the data

By Nicole Karlis
Published June 12, 2021 2:00PM (EDT)
New covid-19 coronavirus mutation (Getty Images)
New covid-19 coronavirus mutation (Getty Images)

Though they are technically not alive, viruses are not unlike living plants or animals. They can be bred, and they can mutate; over months and years, they evolve into new things. At some point in November 2019, there was one human on Earth who had been infected with SARS-CoV-2. Now, the virus has passed through millions of bodies, and replicated trillions of times. It is the nature of RNA viruses to change and evolve gradually — thus, the SARS-CoV-2 virus that infected patient zero has spawned numerous variants as it multiplied through the human population.

"All RNA viruses mutate over time, some more than others," writes Robert Bollinger, a professor of Infectious Diseases at Johns Hopkins University." For instance, flu viruses are particularly prone to mutation, which is why new strains circulate every year.

The novel coronavirus's variants have sprung up all over the world, with some of the most prominent mutations appearing in England, South Africa, Brazil, India and California. As long as the coronavirus keeps spreading, it will keep mutating, which is why public health experts are pushing vaccination as a means to stop the spread and thus the mutations.

"One thing that has to be kept in mind is that the rest of the world is largely not immune, and the rest of the world has not really been vaccinated," said Dr. Charles Chiu, a professor of infectious diseases at the University of California–San Francisco. "The reason why these variants emerge is because you have ongoing transmission, so until we're able to curtail the pandemic globally, we're going to continue to see the emergence of variants."

The ultimate fear, then, is that one of these mutations will render one or more of the vaccines obsolete — thus launching a renewed vaccine arms race against a novel mutant strain. There's no evidence that has happened yet; some variants seem slightly more resistant to some vaccines, but in general the vaccines seem to confer protection against most prominent strains so far.

Still, nobody knows for certain. But Monica Gandhi, infectious disease doctor and professor of medicine at the University of California–San Francisco, is optimistic that vaccines will continue to offer protection against mutant variants — mainly, because of the reason has to do with the strong immune response induced by the vaccines.

"Even if you have a variant that has 13 mutations, like the Delta variant, you're still going to get that lineup of lots of T cells that combat some of those variants," said Gandhi. T cells are a type of roaming white blood cell that attacks and kills pathogens they find in the bloodstreams. "I do think T cell responses from vaccines will work against" these variants, she said.

Researchers and pharmaceutical companies are thus rushing to figure out if that's true. As more and more variants appear, studies into how vaccines work against them follow. Now, according to the Centers for Disease Control and Prevention (CDC), there are five "notable" variants circulating the United States. Here's what each one is, and what we know about vaccine efficacy in each case. 

Variant: B.1.1.7

First identified in the United Kingdom in October 2020, the B.1.1.7 strain is said to be more deadly and more transmissible. It quickly became the most dominant strain in the UK, and is believed to be the cause of a deadly fall surge. It was first identified in the U.S. in December 2020; now, it is the most common source of new infections, according to the CDC.

How the vaccines work against it: According to data published in March 2021, overall efficacy for the AstraZeneca-Oxford COVID-19 vaccine is 61.7 percent against the B117 variant. Separate data from the Pfizer vaccine showed that it has overall 89.5 percent efficiency against the variant 14 days after the second dose. In an in vitro study, Moderna's COVID-19 vaccine produced neutralizing antibodies against the B.1.1.7 variant, according to a Nature study published in March 2021, but there was no specific efficacy percentage provided. Efficacy for the Johnson & Johnson vaccine remains just as strong against B.1.1.7, the company has previously stated, based on data from its Phase 3 clinical trial.

Variant: B.1.351

This variant, which first emerged in Durban, South Africa in December 2020, initially alarmed scientists because the mutation of the virus happened at the SARS-CoV-2 spike protein — the little spikes that emanate from the surface of the virus like spines on a sea urchin — thus, disguising its appearance to the immune system. That was alarming to immunologists, because some vaccines work by training the immune system to recognize the Spike protein; if it is altered, some fear those vaccines may not work as well. In January 2021, health officials first detected it in the United States.

How the vaccines work against it: Unfortunately, according to a study published in the New England Journal of Medicine in May 2021, two shots of the AstraZeneca-Oxford University COVID-19 vaccine were ineffective against mild-to-moderate infections of B.1.351. According to the study, it has a 10.4% effectiveness against the variant. However, none of the people observed in the study with mild-to-moderate infections were hospitalized.

However, a separate study published in May in The New England Journal of Medicine showed that both the messenger RNA vaccines, Pfizer and Moderna, are effective against the variant based on data from Qatar. 

For the Johnson & Johnson vaccine, the single shot is reportedly 57 percent effective against the B.1.351 strain based on data from South Africa. Notably, while some people still had mild to moderate infections, nobody was hospitalized.

Variant: P.1 (also known as the "Gamma" variant)

This variant, which has three mutations to the spike protein, was initially found in travelers from Brazil who were tested during a routine screening at an airport in Japan in January 2021. This variant is believed to be the cause of a resurgence of infections in Brazil in some people who had COVID-19 antibodies, suggesting that this variant can evade natural immunity from a previous infection.

How the vaccines work against it: According to a study published by Oxford University in the journal Cell, the antibody response from the Astrazeneca vaccine in blood samples of people with the P1 variant was reduced three times — but it wasn't as low as the efficacy against the B.1.351 variant. A paper published this week in Nature reported that those who were vaccinated with two doses of the Pfizer–BioNTech COVID-19 vaccine were able to neutralize the P1 variant.

Moderna recently released data from a phase 2 study showing that a single dose of the Moderna vaccine as a booster, in fully vaccinated people, neutralized the P1 variant.

From data collected in South Africa, where the P1 strain has been circulating, experts believe that the single-dose Johnson & Johnson shot is still effective at preventing severe outcomes from the P1 strain, while less effective at preventing mild to moderate infections.

Variants B.1.427 and B.1.429

Both of these strains were identified in California in 2021, and they seem to spread more quickly and lead to more hospitalizations, according to the CDC.

How the vaccines work against them: Unfortunately, there is little information currently about these variants and the effect of vaccines on them. The CDC states that studies suggest that the current authorized vaccines in the U.S. work on these variants, but studies are still ongoing. (This story will be updated as more information about these two variants is revealed through research.)

Variant: B.1.617.2 (known as the "Delta" variant)

According to the CDC, the Delta variant accounts for more than 6 percent of sequenced virus samples in the United States; a month ago it accounted for only slight more than 1 percent of sequenced samples. It was first detected in February 2021 in India, and has been declared a "variant of concern" by the World Health Organization. Experts believe it is more transmissible and can lead to more hospitalizations.

How the vaccines work against it: According to early data published by Public Health England (PHE), the AstraZeneca vaccine was 60 percent effective against the variant after two doses, and the Pfizer vaccine was 88 percent effective.

While there haven't been studies on Johnson & Johnson and Moderna, there is evidence to suggest that the Moderna vaccine can neutralize the Spike protein of this variant. According to the Washington Post, Dr. Anthony Fauci said the protection from the variant with two Moderna shots is likely similar to the effectiveness of the two Pfizer shots.


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Nicole Karlis

Nicole Karlis is a staff writer at Salon. Tweet her @nicolekarlis.

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Covid-19 Explainer Immunology Vaccine Effectiveness