US government scientists are working to make their own strain of coronavirus, a new report reveals - and they may use it to infect willing Americans who volunteer for 'challenge trials' of vaccines, according to Reuters.

Challenge trials are a controversial way to study whether vaccines effectively prevent infections, but they could speed up the process of proving shots work for President Trump's Operation Warp Speed initiative.  

Healthy volunteers would be vaccinated and then intentionally infected with the virus. 

The work to make a strain of SARS-CoV-2 is preliminary and such trials would not replace large-scale, Phase 3 trials such as those now under way in the United States testing experimental COVID-19 vaccines from Moderna Inc and Pfizer, according to a statement emailed to Reuters by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health.

US officials organizing the fight against the pandemic have been under pressure from advocacy groups such as 1 Day Sooner and others that see challenge trials as a way to speed up tests of a COVID-19 vaccine. 

Most vaccine trials rely on inadvertent infection, which can take time to occur.

Some drugmakers, including AstraZeneca and Johnson & Johnson, have said they would consider human challenge trials to test COVID-19 vaccines if needed.

'Should there be a need for human challenge studies to fully assess candidate vaccines or therapeutics for SARS-CoV-2, NIAID has begun investigations of the technical and ethical considerations of conducting human challenge studies,' the agency statement said.