COVID-19 Resource Center

COVID-19 Resource Center

Disclosures: Edwards is an employed by Moderna. Please see the study for all other authors’ relevant financial disclosures.
January 25, 2021
2 min read

Moderna says COVID-19 vaccine protects against variants, but will explore adding booster

Disclosures: Edwards is an employed by Moderna. Please see the study for all other authors’ relevant financial disclosures.
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Moderna said that its COVID-19 vaccine remains protective against newly emerging SARS-CoV-2 variants, including those first identified in the United Kingdom and South Africa.

In experiments, the vaccine demonstrated reduced neutralizing activity against the variant first reported in South Africa, but was still protective, the company said.

COVID vaccine
Moderna’s COVID-19 vaccine is effective against newly emerged COVID-19 strains, including those from the U.K and South Africa.
Credit: Adobe Stock

The vaccine is one of two authorized for use against COVID-19 in the United States. The other shot, developed by Pfizer and BioNTech, also appears to be effective against virus variants, the companies said previously.

Experts expect efficacy data from a third vaccine, developed by Johnson & Johnson, any day. Phase 1/2 findings published in The New England Journal of Medicine this month showed that the vaccine, which is given in one dose, “had an acceptable safety and reactogenicity profile and was immunogenic after a single vaccination” with either a low or high dose, researchers wrote. Specifically, researchers reported detecting neutralizing-antibody titers against wild-type virus in at least 90% of all participants 29 days after one dose of the vaccine.

National Institute of Allergy and Infectious Diseases Director Anthony S. Fauci, MD, said recently that the vaccine could be authorized for use in the U.S. by mid-February.

The emerging variants have caused some consternation among experts, who expect that they could complicate the response in the coming months.

The variants have “raised concerns due to their increased rates of transmission as well as their potential to circumvent immunity elicited by natural infection or vaccination,” Darin K. Edwards, PhD, director of immunology in Moderna’s infectious disease group, and colleagues wrote in an accompanying preprint article that summarized results from in vitro neutralization tests of sera from study participants who received the vaccine as part of a phase 1 clinical trial.

Results of the study showed that the antibody response elicited by the vaccine provided similar levels of neutralization against variants as it did against the initial strain. Moderna noted that there was a sixfold reduction in neutralizing titers observed with the variant first identified in South Africa, known as B.1.351, relative to previously recognized variants. However, neutralizing titer levels with B.1.351 remained higher than those that are expected to be protective, the company said.

“Data from this sample set show mRNA-1273 maintained activity against all circulating strain variants tested to date, and only the B.1.351 variant showed reduced neutralizing titers, as assessed from vaccinated human and NHP sera,” Edwards and colleagues wrote.

Out of “an abundance of caution,” Moderna said it would launch a clinical program to boost immunity to the emerging variants and will test an additional booster dose of the vaccine to study the possibility of increasing the neutralizing titers against emerging strains beyond the existing primary vaccination series. Currently, the vaccine is given in two doses 28 days apart.

Moderna also plans to advance an emerging variant booster candidate against the variant first reported in South African. The booster is being tested in preclinical studies, as well as a phase 1 study in the U.S.

“The emergence of strain variants and the ability of the virus to partially overcome natural or vaccine-induced immunity does serve as a call to action, pointing to the need for continued efforts to vaccinate with the currently approved mRNA regimens to prevent the emergence of future variants that may further evade immunity,” Edwards and colleagues wrote. “In addition, active viral surveillance and testing of protection against new viral variants must continue, and if warranted, new vaccine efforts must be engaged to protect against breakthrough strains.”


Press Release

Sadoff J, et al. N Engl J Med. 2021;doi:10.1056/NEJMoa2034201.

Wu K, et al. bioRxiv. 2021;doi:10.1101/2021.01.25.427948.