The US National Institutes of Health (NIH) has initiated dosing in a new Phase I clinical trial of Moderna’s investigational vaccine candidate, mRNA-1273.351, in adult subjects.

mRNA-1273.351 is designed to provide protection against the B.1.351 SARS-CoV-2 variant.

Led and funded by the NIH unit National Institute of Allergy and Infectious Diseases (NIAID), the trial will have approximately 210 healthy adult subjects at four clinical research sites in the US.

NIAID director Anthony Fauci said: “The B.1.351 SARS-CoV-2 variant, first identified in the Republic of South Africa, has been detected in at least nine states in the US.

“Preliminary data show that the Covid-19 vaccines currently available in the US should provide an adequate degree of protection against SARS-CoV-2 variants.

“However, out of an abundance of caution, NIAID has continued its partnership with Moderna to evaluate this variant vaccine candidate should there be a need for an updated vaccine.”

In the study, 60 adults who have received the mRNA-1273 vaccine and 150 individuals aged 18 to 55 who have not received any Covid-19 vaccine will be enrolled.

The trial will assess the safety and reactogenicity of the vaccine candidate and its capacity to stimulate an immune response.

The trial investigators plan to fully enrol subjects by the end of this month and anticipate the results to inform further analysis of vaccine variant strategies, should an updated vaccine be needed.

Authorised by the US Food and Drug Administration for emergency use in the US, the mRNA-1273 vaccine is co-developed by NIAID investigators and Moderna. It is indicated for preventing Covid-19 in adults aged 18 and above and is administered as two 100mcg doses given 28 days apart.

The variant vaccine candidate mRNA-1273.351 differs from the Moderna vaccine currently authorised, as it provides instructions for making the SARS-CoV-2 spike that incorporates key mutations in the B.1.351 virus variant.

Apart from this trial, NIAID Vaccine Research Center investigators are partnering with Moderna to analyse mRNA-1273.351 in animal models.