The vaccine is about 66 per cent effective overall at preventing moderate to severe Covid-19, a report on Wednesday by the Food and Drug Administration confirmed.
It will now go forward to a panel of FDA experts who will debate if the evidence is strong enough to recommend the vaccine.
The FDA is expected to make a final decision within days.
If the FDA clears the J&J shot for US use, it won't boost vaccine supplies significantly right away. Only a few million doses are expected to be ready for shipping in the first week.
The company aims to make one billion doses this year. The UK has ordered 30 million doses of the jab, while the US has ordered 100 million and Canada 38 million.
J&J tested its single-dose option in 44,000 people in the US, South America and South Africa. J&J previously announced the vaccine worked better in the US - 72 per cent effective against moderate to severe Covid-19, compared with 66 per cent in Latin America and 57 per cent in South Africa.
Still, in every country it was highly effective against the most serious symptoms, and early study results showed no hospitalisations or deaths starting 28 days after vaccination.
It comes as England’s deputy chief medical officer rejected salls for the Government to speed up the easing of lockdown.
Prime Minister Boris Johnson has come under pressure from a vocal group of Tory backbenchers to ease all restrictions by the end of April, rather than follow the cautious approach which will see some of England’s curbs continue until June 21 at the earliest.
But Professor Jonathan Van-Tam insisted the five-week gap between different stages is necessary to monitor the impact on infections and “I would rather do this once and get it right and not have to make any U-turns”.
He also acknowledged concerns about vaccine hesitancy in black and minority ethnic groups, and stressed that health and care staff should have a Covid-19 jab as part of their “professional responsibility” to patients.
He acknowledged there has been a “slowdown” in the vaccine rollout due to supply fluctuations but insisted he is confident that the targets of giving a first dose to the top nine priority groups by mid-April and to all adults by the end of July will be met.
