Multibillionaire philanthropist Bill Gates says a third shot of the vaccine might be needed to battle COVID-19 in the future, as there are concerns that current vaccines are less effective against the new virus variants, such as those from South Africa and Brazil.

“The discussion now is do we just need to get a super high coverage of the current vaccine, or do we need a third dose that’s just the same, or do we need a modified vaccine?” Gates told CBS Evening News.

“All five of the companies that have US vaccines are looking at making that modification and adding that in so that people who’ve already had two shots might need to get a third shot,” he said, adding that it’s “reasonably likely” that Americans will require a “tuned vaccine” as additional protection from the new variants.

Gates also said that the vaccine made by AstraZeneca has a “challenge” with the new coronavirus variant. He warned that additional shots may be necessary in the future: “probably not yearly, but as long as it’s out there.”

Earlier this month, the chief of the World Health Organisation, Tedros Adhanom Ghebreyesus, admitted existing coronavirus vaccines might be ineffective in fighting the new highly-transmissible strains and urged manufacturers to upgrade their vaccines.

Bill Gates and his wife Melinda founded the Bill & Melinda Gates Foundation, which specialises in a wide range of public health projects. It funds the fight against transmissible diseases, as well as developing vaccines.

According to data collected by the Johns Hopkins University, COVID-19 cases in the US have topped 27,827,801 with 490,717 deaths.