By Peter Loftus 

Moderna Inc. said Monday its Covid-19 vaccine appeared to be protective against emerging variants of the coronavirus in laboratory tests, but as a precaution it will start testing whether a booster shot improves immune responses and is developing a new vaccine targeting the strain first identified in South Africa.

The company said its vaccine produced immune-system agents known as neutralizing antibodies against emerging virus variants tested, including strains first identified in the U.K. and South Africa.

These new strains appear to spread more easily from person to person, and there are signs that the U.K. variant is more deadly than earlier forms of the virus.

Moderna said its vaccine induced antibody production against the strain first identified in the U.K., known as B.1.1.7, at levels comparable to prior variants. Yet antibodies decreased sixfold against the strain first identified in South Africa, known as B.1.351, according to a paper posted on the preprint server bioRxiv, which hasn't yet gone through the standard peer-review process. Researchers from both Moderna and the National Institutes of Health's Vaccine Research Center conducted the analyses.

Even with the decrease, Moderna said, the vaccine-induced antibody response against the B.1.35 variant remained above levels that are expected to be protective. The company said it expects its standard, two-dose vaccine to be protective against the emerging strains to date.

It will test, however, whether adding a booster dose of its original vaccine can boost antibody levels against emerging viral strains.

The company is also developing a new version of the vaccine that targets more specifically the mutations in the South African variant and will test whether giving that as a booster shot induces a better immune response.

The company plans to start within a couple of months a Phase 1 study of the booster shot aimed at the South African variant.

"In the event that this virus continues to mutate in this direction, and a year from now is still circulating in some way, we think it's prudent that we have tools like a booster vaccine to address that," Moderna President Stephen Hoge said in an interview.

Moderna said it expects that its booster shot -- whether the original vaccine or the one targeting the variant first identified in South Africa -- could be given in combination with other vaccines.

The coronavirus variant first identified in South Africa has several mutations in its so-called spike protein, which is found on the surface of the virus. Moderna's vaccine and most others are designed around the spike protein or its genetic code as a way to induce an immune response to the virus, so mutations in the protein have the potential to hurt the performance of a vaccine.

Moderna's modified vaccine is designed to trigger the production of the spike protein specific to the South African variant, which in turn induces an immune response.

The company believes it can quickly design and manufacture the modified vaccine and have it ready for initial human testing at a faster pace than its work last year on the original vaccine. Last year, it shipped the first batch for testing about six weeks after selecting the initial design, and the first human study started within two months.

"I believe we should be able to go even faster now," Chief Executive Stephane Bancel said last week during an interview for the WSJ Executive Membership Series. "If in the future we encounter a mutation that requires a new vaccine, we could very quickly, in a matter of a month or so, get a new vaccine out."

Mr. Bancel said he didn't think regulators would require such a vaccine to go through the full series of human studies since it would have the same underlying gene-based technology as the original vaccine.

Moderna's move points to the potential that Covid-19 vaccines will have to be modified -- and possibly given as repeat doses to people previously vaccinated -- to address a changing virus.

"We may have to begin thinking about this like influenza vaccines and start rolling out regular annual vaccinations," with modified vaccines that target different strains, said Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine in Texas.

Pfizer Inc. and BioNTech SE, who make the only other Covid-19 vaccine authorized for use in the U.S., are continuing to run lab studies of their vaccine against new variants, a Pfizer spokeswoman said.

Last week, Pfizer and BioNTech said their vaccine appeared to be protective against the U.K. virus strain, based on lab studies.

"The virus is evolving and it's getting fitter and better at what it needs to do," said Dr. Hoge, Moderna's president. "And both the South African and the U.K. strains, we're seeing clearly increases in transmission, and the potential for infectivity."

Moderna shares were ahead 11% at $145.87 in morning trading Monday.

--Jared S. Hopkins contributed to this article.

Write to Peter Loftus at


(END) Dow Jones Newswires

January 25, 2021 11:50 ET (16:50 GMT)

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