The US just launched the first study testing a version of Moderna's coronavirus vaccine tailored to fight a concerning variant

• The first clinical-trial testing a variant-specific COVID-19 shot launched Wednesday.
• The NIH-sponsored study will test an updated version of Moderna's coronavirus vaccine.
• It's designed to fight the B.1.351 strain first identified in South Africa.

The first clinical trial to test an updated version of a coronavirus vaccine began Wednesday.

US researchers are testing a shot made by the Massachusetts biotech Moderna that's tailored to neutralize a concerning variant of the novel coronavirus. The research is the latest escalation in society's battle against variants of the virus. Experts worry that specific mutations in the virus' spike protein, the target of coronavirus vaccines, could partially lower the protection vaccines give.

The variant first identified in South Africa, called the B.1.351 variant, has been especially concerning. Data from testing in petri dishes found this version of the virus led to a significant decrease in neutralizing antibodies, the virus-fighting proteins generated by the vaccine. While the leading vaccines are still believed to help protect against this strain, virologists fear the reduced immune response could lead to shorter durability of protection.

In response, leading vaccine developers have started research on versions of their shots tailored against B.1.351. Moderna has become the first to start human testing of a variant-focused shot, with this study being run by the US National Institutes of Health.

NIH researchers expect to enroll 210 healthy American adults in this study by the end of April in the Atlanta, Cincinnati, Seattle, and Nashville, Tennessee, areas. Sixty of those volunteers will be selected from a previous study of Moderna's original COVID-19 shot.

The study will test a variety of dosing options, including different dose strengths and the number of shots, either two or three.

NIH did not specify when results were expected, and Moderna did not immediately respond to a request for comment on the timeline. The Jefferies biotech analyst Michael Yee estimated Tuesday in a note to investors that data for this variant-specific vaccine should be "likely coming in the next few months."