While the two-dose regimen of the Moderna Covid-19 vaccine is expected to be protective against emerging strains detected to date, the company on Monday said it is also working on a Covid-19 booster shot to protect against a new variant first identified in South Africa.
The company said that it is advancing the booster vaccine candidate, mRNA-1273.351, into preclinical studies and a Phase 1 study in the US to evaluate the immunological benefit of boosting with strain-specific spike proteins.
This is despite the fact that vaccination with the Moderna Covid-19 vaccine produced neutralising titers against all key emerging variants tested, including B.1.1.7 and B.1.351, first identified in the UK and South Africa, respectively, the company said, citiing a lab study.
However, the company also said it will test an additional booster dose of its Covid-19 vaccine (mRNA-1273) to study the ability to further increase neutralising titers against emerging strains beyond the existing primary vaccination series.
“As we seek to defeat the Covid-19 virus, which has created a worldwide pandemic, we believe it is imperative to be proactive as the virus evolves. We are encouraged by these new data, which reinforce our confidence that the Moderna Covid-19 vaccine should be protective against these newly detected variants,” Stephane Bancel, Chief Executive Officer of Moderna, said in a statement.
“Out of an abundance of caution and leveraging the flexibility of our mRNA platform, we are advancing an emerging variant booster candidate against the variant first identified in the Republic of South Africa into the clinic to determine if it will be more effective to boost titers against this and potentially future variants.”
First detected in September 2020 in the UK, the SARS-CoV-2 B.1.1.7 variant has seventeen mutations in the viral genome with eight mutations located in the spike (S) protein.
The B.1.351 variant, first detected in South Africa, has ten mutations located in the spike (S) protein.
Both variants have spread at a rapid rate and are associated with increased transmission and a higher viral burden after infection.
The in vitro study assessed the ability of Moderna’s Covid-19 vaccine, mRNA-1273, to elicit potently neutralising antibodies against the new SARS-CoV-2 variants.
The results showed that the vaccine appeared to be less protective against the variant identified in South Africa.
This study was conducted in collaboration with the Vaccine Research Center (VRC) at the National Institute of Allergy and Infectious Diseases (NIAID), part of the US National Institutes of Health (NIH).
The manuscript has been submitted as a preprint to bioRxiv and will be submitted for peer-reviewed publication, Moderna said.
Moderna said it expects that its mRNA-based booster vaccine (whether mRNA-1273 or mRNA-1273.351) will be able to further boost neutralising titers in combination with all of the leading vaccine candidates.