The US Food and Drug Administration on Tuesday released guidance for approving a coronavirus vaccine, saying the vaccine has to prevent or decrease disease severity in at least 50 per cent of people who are inoculated.
More than 100 vaccines are being tested worldwide against the virus, which has claimed over 126,100 lives in the United States, according to Reuters.
The Trump administration in May announced a programme called "Operation Warp Speed" to speed up the development of COVID-19 therapeutics and vaccines, as the country has none approved for treating COVID-19.
Several companies such as Moderna Inc, Pfizer Inc and AstraZeneca Plc are in the race to develop a vaccine.
"While the FDA is committed to expediting this work, we will not cut corners in our decisions," the FDA said on Tuesday.
Experts have said it could take 12 to 18 months for a vaccine to be developed.
Vaccine developers have also been asked for data to support use during pregnancy and to show safety and effectiveness in children, the health regulator said.
"The guidelines are pretty standard, they look pretty much like influenza vaccine guidelines," Gregory Poland, director of Mayo Vaccine Research Group said.
"I don't think that's a high bar. I think that's a low to maybe an appropriate bar for a first-generation COVID-19 vaccine."
Flu vaccines are 30 per cent-70 per cent effective in any given year, according to Jefferies analyst Michael Yee. The guidelines could be seen as a relatively high bar given the urgency to accelerate availability of a vaccine, Yee added.
Dr Anthony Fauci, the United States government's top infectious diseases expert, cautioned that there is no guarantee of a safe and effective vaccine.