The United States is likely to have enough safe and effective Covid-19 vaccines available to inoculate the most vulnerable Americans by the end of 2020, Health and Human Services Secretary Alex Azar has said.

The US government is “cautiously optimistic” that one or two vaccines, likely from Pfizer Inc or Moderna Inc, will be available by the end of the year and can begin to be distributed to Americans, officials said during a news conference.

Azar said he expects all seniors, healthcare workers, and first responders will be able to receive a vaccine as soon as January, with the rest of the American public able to get a vaccine by April.