Clinical trials of the modified vaccine may begin within a few weeks.
The pharmaceutical company Moderna said it produced the first batch of doses of a new vaccine with increased efficacy against a new strain of coronavirus that proved more resistant to the company’s original vaccine.
The Cambridge, Massachusetts-based company said it sent doses of the new vaccine to the National Institutes of Health to conduct the first human trial of the modified vaccine. It can start within a few weeks.
The new vaccine, codenamed mRNA-1273.351, is designed to provide a higher degree of protection against a variant of the virus that was first detected in South Africa but has since spread to other countries.
Other companies, including Pfizer and Johnson & Johnson, have said they are also modifying their vaccines or working on boosters that better match the new variants of the virus.