A registered pharmacist technician carefully fills the Pfizer-BioNTech COVID-19 mRNA vaccine at a vaccine clinic during the COVID-19 pandemic in Toronto on December 15, 2020. THE CANADIAN PRESS/Nathan Denette
Preliminary lab tests suggest Moderna's COVID-19 vaccine produced a weaker immune response to the South African variant of the virus.
So out of an abundance of caution, Moderna will test a possible booster dose against it.
Vaccine manufacturers have been testing their shots against variants, including two that first emerged in Britain and South Africa.
Pfizer has previously reported that its shot appears effective against the strain from Britain.
Although some other research has raised questions about the vaccine's effectiveness on South African variant.