The United States approved Johnson & Johnson's Covid vaccine for emergency use on Saturday, giving the country a third chance to fight the epidemic that has taken the lives of more than 500,000 Americans.
Before approving it, the Food and Drug Administration (FDA) reported that the single-shot vaccine is highly successful in preventing extreme Covid-19, including newer versions.
In a tweet, US President Joe Biden said, "This is exciting news for all Americans, and a promising step in our efforts to put an end to the crisis."
However, he urged Americans to maintain caution with anti-virus measures such as social distancing, warning that new virus variants posed a threat.
"But we can't relax our guard now or believe victory is a foregone conclusion," he said.
A third vaccine is seen as crucial to rising the immunization rate in the United States, where the coronavirus has claimed the lives of over 500,000 people.
The J&J vaccine's effectiveness against the serious disease was 85.9% in the United States, 81.7 percent in South Africa, and 87.6 percent in Brazil in large clinical trials.
The efficacy against extreme Covid-19 was 85.4 percent overall among 39,321 participants from all continents, but it declined to 66.1 percent when mild types of the disease were included.
Importantly, studies of different population groups showed no major variations in age, race, or the existence of underlying conditions.
By June, 100 million doses would have been released.
After Pfizer's and Moderna's vaccines were provisionally accepted in December, the J&J vaccine is the third to be approved in the United States.
Over 65 million people in the United States have received at least one dose of either the Pfizer or Moderna vaccines; however, unlike those vaccines, the J&J vaccine only requires one dose and is kept at refrigerator temperatures, providing logistical and practical benefits.
The J&J shot tends to be less protective than the two-shot regimens provided by Pfizer and Moderna, which both have a 95 percent efficacy against all types of Covid-19 from the classic coronavirus strain.
However, all three have been shown to provide complete defense against hospitalization and death.
The two earlier vaccines were tested months before the introduction of "variants of concern" that could impact effectiveness, according to Nirav Shah, director of the Maine Center for Disease Control and Prevention, telling The Washington Post that the Pfizer and Moderna findings were not a "apples to apples" contrast with the J&J shot.
Based on preliminary results, the J&J vaccine may be effective against asymptomatic infection, though the company indicated that further research is required.
To pass the gene for a crucial protein of the coronavirus into human cells, the J&J vaccine uses a common-cold-inducing adenovirus that has been genetically engineered so that it can't replicate.
(This story was not edited by staff and is published from a syndicated feed, except for the headline.)