New York, Feb 25 (IANS): US-based drugmaker Moderna said that it has completed manufacturing of clinical trial material for its variant-specific vaccine candidate against the SARS-CoV-2 variant known as B.1.351 -- first identified in the Republic of South Africa.

The company has shipped doses to the National Institutes of Health (NIH) for a Phase 1 clinical trial that will be led and funded by the NIH's National Institute of Allergy and Infectious Diseases (NIAID).

"As we seek to defeat Covid-19, we must be vigilant and proactive as new variants of SARS-CoV-2 emerge. Leveraging the flexibility of our mRNA platform, we are moving quickly to test updates to the vaccines that address emerging variants of the virus in the clinic," Stéphane Bancel, Chief Executive Officer of Moderna, said in a statement.

While initial data confirms that the Moderna Covid-19 vaccine (mRNA-1273) provides neutralizing activity against variants of concern, out of an abundance of caution, the pharmaceutical company is pursuing two strategies against these variants, subject to US Food and Drug Administration (FDA) review.

First, the company is evaluating booster doses of vaccine to increase neutralizing immunity against the variants of concern. Moderna plans to evaluate three approaches to boosting, including a variant-specific booster candidate, mRNA-1273.351, based on the B.1.351 variant, at the 50 µg dose level and lower.

A multivalent booster candidate, mRNA-1273.211, which combines mRNA-1273, Moderna's authorized vaccine against ancestral strains, and mRNA-1273.351 in a single vaccine at the 50 µg dose level and lower.

A third dose of mRNA-1273, the Moderna Covid-19 vaccine, as a booster at the 50 µg dose level.

The company has already begun dosing this cohort with the booster.

Second, the company plans to evaluate mRNA-1273.351 and mRNA-1273.211 as a primary vaccination series for those who are seronegative. These candidates will be evaluated in a two-dose series at the 100 µg dose level and lower.

A letter to the editor published in the New England Journal of Medicine showed vaccination with the Moderna Covid-19 vaccine produced neutralizing titers against all key emerging variants tested, including B.1.1.7 and B.1.351, first identified in the UK and Republic of South Africa, respectively.

The study showed no significant impact on neutralizing titers against the B.1.1.7 variant relative to prior variants. A six-fold reduction in neutralizing titers was observed with the B.1.351 variant relative to prior variants.