An FDA official has told a US Senate hearing the regulator will only approve COVID-19 vaccines that are 50 per cent more effective than placebo.
FDA Commissioner Stephen Hahn said that level of efficacy would put a COVID-19 vaccine on par with the annual flu shot. This compares to some childhood vaccines, including measles, that are 97-98 per cent effective.
The Wall Street Journal also reported the FDA will not compromise its standards on the consideration of any vaccine.
The discussion on efficacy comes as more companies progress investigational vaccines to human trials.
According to BIO's COVID-19 pipeline tracker, there are now 19 vaccines in human trials, including three in phase three.
Dr Anthony Fauci, who is the director of the US government's National Institute of Allergy and Infectious Diseases, recently said he expects any vaccine to be 70-75 per cent effective.
Dr Fauci said the US was unlikely to achieve 'herd immunity' given around 30 per cent of people said they would not accept vaccination.
A recent study found halting the spread of COVID-19 would require a vaccine to be at least 70 per cent effective and it would need to be administered to 60 per cent of the population within three months.