On Tuesday, top White House science advisor David Kessler told U.S. senators that if they prove necessary, COVID-19 vaccine booster shots will be provided for free to Americans. “We do have the funds to purchase the next round and to assure if there are boosters that they are free just as the last round,” said Kessler, who left open the possibility of a “transition back to a commercial market” for immunizations after 2022. The U.S., Kessler said, also needs to speed up the development of oral antiviral drugs that can help fight the virus. “People who are immunosuppressed, who do not mount an immune response for a number of reasons, or choose not to be vaccinated, will continue to be vulnerable, and we need options for them,” said Kessler.

A booster shot from Moderna is already in clinical trials and, according to the company, has shown encouraging efficacy against some of the virus variants. And, of course, there is a growing body of evidence that the existing vaccines are effective against COVID-19 mutations.