A nurse in New York became the first person in the United States to receive the coronavirus vaccine Monday.
Sandra Lindsay, a critical care nurse at the Long Island Jewish Medical Center, received the Pfizer-BioNTech shot live on television shortly before 9.30am (1430 GMT).
"First Vaccine Administered. Congratulations USA! Congratulations WORLD!" President Donald Trump tweeted.
Lindsay said the jab "didn't feel any different from taking any other vaccine."
"I feel great. I feel relieved," she said.
"I hope this marks the beginning of the end of the very painful time in our history. I want to instil public confidence that the vaccine is safe.
"We're in a pandemic so we all need to do our part," Lindsay added.
Governor Andrew Cuomo, watching the landmark moment via video-link, told Lindsay he hoped the vaccine would give her and other frontline health care workers "a sense of security and safety."
"It's going to take months before the vaccine hits critical mass. So, this is the light at the end of the tunnel, but it's a long tunnel," he said, reminding people to keep following social distancing guidelines.
Covid-19 has ravaged the United States.
More than 299,000 Americans have been killed by the virus, including over 35,000 residents of New York state.