COVID vaccines might not work as well on new SARS-CoV-2 variants

Syringes filled with doses of the AstraZeneca vaccine against COVID-19 lie on a table at a private medical practice before inoculations as part of a pilot project in the state of Brandenburg during the coronavirus pandemic on March 03, 2021 in Senftenberg, Germany. (Credit: Getty Images)

Three new, fast-spreading variants of the virus that causes COVID-19 can evade antibodies that work against the original form that sparked the pandemic, new research shows.

With few exceptions, whether the antibodies were produced in response to vaccination or natural infection, or were purified antibodies intended for use as drugs, researchers found they needed more antibody to neutralize the new variants.

The findings, from laboratory-based experiments, suggest that COVID-19 drugs and vaccines developed thus far may become less effective as the new variants become dominant, as experts say they inevitably will. The researchers looked at variants from South Africa, the United Kingdom, and Brazil.

“We’re concerned that people whom we’d expect to have a protective level of antibodies because they have had COVID-19 or been vaccinated against it, might not be protected against the new variants,” says senior author Michael S. Diamond, professor of medicine at Washington University in St. Louis.

“There’s wide variation in how much antibody a person produces in response to vaccination or natural infection. Some people produce very high levels, and they would still likely be protected against the new, worrisome variants.

“But some people, especially older and immunocompromised people, may not make such high levels of antibodies. If the level of antibody needed for protection goes up tenfold, as our data indicate it does, they may not have enough. The concern is that the people who need protection the most are the ones least likely to have it.”

Viruses are always mutating

The virus that causes COVID-19, known as SARS-CoV-2, uses a protein called spike to latch onto and get inside cells. People infected with SARS-CoV-2 generate the most protective antibodies against the spike protein.

Consequently, spike became the prime target for COVID-19 drug and vaccine developers. The three vaccines the Food and Drug Administration (FDA) has authorized for emergency use in the US—made by Pfizer/BioNTech, Moderna, and Johnson & Johnson—all target spike. And researchers selected potent anti-spike antibodies for development into antibody-based drugs for COVID-19.

Viruses are always mutating, but for nearly a year the mutations that arose in SARS-CoV-2 did not threaten this spike-based strategy. Then, this winter, fast-spreading variants were detected in the United Kingdom, South Africa, Brazil, and elsewhere. Sparking concern, the new variants all carry multiple mutations in their spike genes, which could lessen the effectiveness of spike-targeted drugs and vaccines now being used to prevent or treat COVID-19. Researchers gave the most worrisome new variants the names of B.1.1.7 (from the UK), B.1.135 (South Africa), and B.1.1.248, also known as P.1 (Brazil).

To assess whether the new variants could evade antibodies made for the original form of the virus, Diamond and colleagues, including first author Rita E. Chen, a graduate student in Diamond’s lab, tested the ability of antibodies to neutralize three virus variants in the laboratory.

The researchers tested the variants against antibodies in the blood of people who had recovered from SARS-CoV-2 infection or had received the Pfizer vaccine. They also tested antibodies in the blood of mice, hamsters, and monkeys that had received an experimental COVID-19 vaccine, developed at Washington University School of Medicine, given through the nose.

The B.1.1.7 (UK) variant could be neutralized with similar levels of antibodies as were needed to neutralize the original virus. But the other two variants required from 3.5 to 10 times as much antibody for neutralization.

Then, they tested monoclonal antibodies: mass-produced replicas of individual antibodies that are exceptionally good at neutralizing the original virus. When the researchers tested the new viral variants against a panel of monoclonal antibodies, the results ranged from broadly effective to completely ineffective.

Continual antibody screening

Since each virus variant carried multiple mutations in the spike gene, the researchers created a panel of viruses with single mutations so they could parse out the effect of each mutation. Most of the variation in antibody effectiveness could be attributed to a single amino acid change in the spike protein.

This change, called E484K, was found in the B.1.135 (South Africa) and B.1.1.248 (Brazil) variants, but not B.1.1.7 (UK). The B.1.135 variant is widespread in South Africa, which may explain why one of the vaccines tested in people was less effective in South Africa than in the US, where the variant is still rare, Diamond says.

“We don’t exactly know what the consequences of these new variants are going to be yet,” says Diamond, also professor of molecular microbiology and of pathology and immunology. “Antibodies are not the only measure of protection; other elements of the immune system may be able to compensate for increased resistance to antibodies. That’s going to be determined over time, epidemiologically, as we see what happens as these variants spread.

“Will we see reinfections? Will we see vaccines lose efficacy and drug resistance emerge? I hope not. But it’s clear that we will need to continually screen antibodies to make sure they’re still working as new variants arise and spread and potentially adjust our vaccine and antibody-treatment strategies.”

The study appears in Nature Medicine. Additional coauthors are from the University of Texas Medical Branch and Washington University in St. Louis.

Funding came from the National Institutes of Health, the Defense Advanced Research Project Agency, the Dolly Parton COVID-19 Research Fund at Vanderbilt University, the Helen Hay Whitney Foundation, the Sealy & Smith Foundation, the Kleberg Foundation, the John S. Dunn Foundation, the Amon G. Carter Foundation, the Gilson Longenbaugh Foundation, the Summerfield Robert Foundation, the American College of Gastroenterology, the EPA Cephalosporin Early Career and Teaching Fellowship, and the Townsend-Jeantet Charitable Trust.

Source: Washington University in St. Louis