Moderna Plans to Test Booster Shot Against South Africa Strain

(Bloomberg) -- Moderna Inc. says it plans to begin human studies of a booster shot for its Covid-19 vaccine to help it protect against a more-transmissible South Africa virus variant, after a lab test showed the shot may be less potent against that strain.

In lab tests conducted with the National Institute of Allergy and Infectious Diseases, Moderna says its vaccine produced six-fold lower levels of neutralizing antibodies against the South Africa variant called B.1.351 than it did against the original Covid-19 strain.

Even with the lower antibody levels, its existing vaccine should still protect against people who are exposed to the South Africa strain, Moderna said in a statement. At the reduced levels, the shot produces neutralizing antibody levels “that remain above” levels that protect monkeys.

But the study results could indicate that immunity will wane faster, the company said in a statement.

Meanwhile, Moderna said there was no reduction in antibodies against the rapidly spreading U.K. variant called B.1.1.7. That variant is widespread in the U.K. and is expected the become the dominant strain.

The South Africa strain is “the one we were concerned about based on prior reports,” said Tal Zaks, Moderna’s chief medical officer, in an interview.