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Moderna is pressing forward with a modified version of its Covid-19 vaccine meant to protect against an emerging strain of the virus, the company said Wednesday, planning to start a clinical trial as soon as regulators give the green light.

Laboratory tests have suggested that Moderna’s authorized vaccine confers less protection against the variant, known as B.1.351, than it does against other strains. Pfizer has reported similar findings with its vaccine, and human trials conducted by Johnson & Johnson and Novavax suggest vaccines designed for the original strain of SARS-CoV-2 are less effective against B.1.351 as well.


Moderna said it is seeking to test the novel vaccine on its own and as a combined shot with its current vaccine. It also plans to test whether giving a booster of the current vaccine on its own will give enhanced protection against new variants of the virus that causes Covid-19.

The company said it has shipped doses of its novel vaccine to the National Institutes of Health and is awaiting Food and Drug Administration approval to begin clinical trials.

It will test the boosters in patients who have already received its vaccine in clinical trials, using a dose of 50 micrograms, which is half the strength of its existing Covid-19 vaccine. It also plans to test both the vaccine targeted at the variant and the combination vaccine in volunteers who have not yet been vaccinated.


The FDA has said that it is willing to authorize booster shots based on small clinical trials, accepting data on how well they prime the immune system rather than holding out for long-term results on protecting against Covid-19.

Separately, Moderna said Wednesday it is bolstering its worldwide manufacturing capacity, anticipating a sustained demand for Covid-19 boosters in the coming years. The company said it will be able to manufacture about 1.4 billion 100-microgram doses in 2022. If the 50-microgram booster shots prove to be effective, that output could reach beyond 2 billion doses, it added.

Moderna expects to manufacture about 700 million doses in 2021 and said it is “exploring other approaches” that may push that number up to 1 billion. To date, the company has shipped about 60 million doses of its original vaccine, more than 90% of which have gone to the U.S. government. The U.S. has ordered 300 million doses of Moderna’s vaccine, which the company expects to deliver by the end of July.

Pfizer and BioNTech, which developed a similar Covid vaccine, have said they expect to produce 2 billion doses this year.

“We look forward to beginning the clinical study of our variant booster and are grateful for the NIH’s continued collaboration to combat this pandemic,” Stéphane Bancel, Moderna’s CEO, said in a statement.

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