Moderna Finds COVID-19 Vaccine Still Protects Against Emerging Strains

Moderna says tests show that its COVID-19 vaccine offers protection against new variants of the coronavirus but that the vaccine is more effective against the variant first identified in the U.K. than the one found in South Africa. As a result, Moderna will test booster doses of its vaccine, including one that would be tailored to fight strains that have recently emerged.

The newly identified strains have caused alarm, as health officials in the U.K. and South Africa say the strains appear to spread more easily than older variants of the coronavirus. They emerged in recent months, even as vaccines from Moderna and Pfizer-BioNTech raised hopes in the fight against the COVID-19 pandemic.

Moderna says that at current dosage levels, its COVID-19 vaccine regimen "is expected to be protective against emerging strains detected to date." But the company also says that when its vaccine was used against the variant initially found in South Africa, known as B.1.351, the vaccine produced levels of virus-fighting antibody titers that were around sixfold less than when it's used against other variants.

"These lower titers may suggest a potential risk of earlier waning of immunity to the new B.1.351 strains," Moderna said.

As for the variant found in the U.K., known as B.1.1.7, the company says it found "no significant impact on neutralizing titers against the B.1.1.7 variant relative to prior variants."

The findings result from lab studies in which Moderna scientists tested the ability of samples of blood serum from eight vaccine clinical trial participants to fight off the coronavirus. The studies also used samples of serum from nonhuman primates.

Moderna says that out of "an abundance of caution," it will launch at least two clinical efforts seeking to boost immunity to emerging coronavirus variants.

The first step relies on the same messenger RNA vaccine that the Food and Drug Administration formally authorized last month. But in a new round of tests, the company wants to see if an additional booster dose of the vaccine will ramp up defenses against emerging strains beyond what the current regimen provides.

In the second part of the company's plan, it's developing a new booster vaccine candidate that it will put into a phase 1 study in the U.S. "to evaluate the immunological benefit of boosting with strain-specific spike proteins."

Moderna believes its booster candidate could add protections against the coronavirus when used "with all of the leading vaccine candidates," not just its own vaccine.

"As we seek to defeat the COVID-19 virus, which has created a worldwide pandemic, we believe it is imperative to be proactive as the virus evolves," Moderna CEO Stéphane Bancel said in a statement about the plan. "We are encouraged by these new data, which reinforce our confidence that the Moderna COVID-19 Vaccine should be protective against these newly detected variants."

Both the variants found in the U.K. and South Africa have mutations that set them apart from the original SARS-CoV-2 coronavirus. But the one first seen in South Africa has caused particular alarm. That strain has more mutations in its spike protein than the one from the United Kingdom. It also "may be capable of evading the body's immune system" — raising the risk of reinfection, as NPR's Michaeleen Doucleff recently reported.

Several mutations that were found in the South African strain are also present in a variant that was identified this month in Brazil.

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