(WTVO) — Billionaire Bill Gates is warning a third shot of the COVID-19 vaccine may be needed to prevent the spread of new virus variants.

"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 U.S. 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. "I think it's reasonably likely that we will have a tuned vaccine just to make absolutely sure that as these variants hit the U.S. that they're not escaping from vaccine protection."

The head of the food and drug administration also said that booster shots may be needed if the vaccines become weaker against newer variants in the future.