Chinese hackers targeted the biotech firm Moderna earlier this year, a company that announced a COVID-19 vaccine candidate in January.
That's according to a U.S. security official who exclusively spoke to Reuters, who says the hackers were backed by Beijing.
Moderna's vaccine candidate is one of the earliest and biggest bets by the Trump administration to fight the global pandemic.
This comes after the Justice Department last week revealed an indictment against two Chinese nationals accused of spying.
The indictment listed three targets based in the U.S. working on COVID-19 research, one of which was known to be working on a vaccine in January.
Moderna confirmed to Reuters that it had been in contact with the FBI and was made aware of quote "information reconaissance activities" by the group in last week's indictment.
The federal government is supporting development of the company's vaccine with nearly half a billion dollars -- and helping Moderna launch a clinical trial of up to 30,000 people beginning this month.
China is also racing to develop a vaccine, bringing together its state, military and private sectors to combat a disease that has killed over 660,000 people worldwide.
The Chinese government has consistently denied any role in hacking incidents across the globe.
The spokesperson for China's embassy to the U.S. did not address specific questions sent by email.
The two other medical companies mentioned in the indictment are firms based in California and Maryland, which would match Gilead Sciences and Novavax.
Both companies declined to comment on specific cybersecurity matters.