The United States has given emergency authorisation to Johnson & Johnson's COVID-19 vaccine. AFP/Justin Tallis
WASHINGTON - The United States on Saturday authorised Johnson & Johnson's COVID-19 vaccine for emergency use, giving the nation a third shot to battle the outbreak that has killed more than 500,000 Americans.
"This is exciting news for all Americans, and an encouraging development in our efforts to bring an end to the crisis," US President Joe Biden said in a statement.
But he urged Americans to remain vigilant with anti-virus curbs such as social distancing, warning that new variants of the virus still posed a threat.
"But we cannot let our guard down now or assume that victory is inevitable," he said.
A third vaccine is seen as a vital means to ramp up the immunisation rate in the United States, where more than 500,000 people have lost their lives to the coronavirus.
The J&J vaccine is the third to be greenlighted in the United States after Pfizer's and Moderna's were provisionally approved in December.
Over 65 million people in America have so far received at least one shot of either the Pfizer or Moderna vaccines -- but unlike those, the J&J vaccine requires just one dose, and is stored at fridge temperatures, offering logistical and practical advantages.
The J&J shot appears less protective than Pfizer and Moderna's two-shot regimens, which both have an efficacy of around 95 percent against all forms of COVID-19 from the classic coronavirus strain.
All three have been shown to fully protect against hospitalisations and death, however.