"These actors have been observed attempting to identify and illicitly obtain valuable intellectual property and public health data related to vaccines, treatments, and testing from networks and personnel affiliated with Covid-19-related research," they said.
"China's efforts to target these sectors pose a significant threat to our nations response to Covid-19," they said.
The two organizations gave no evidence or examples of their allegation against Beijing. But they urged "all organizations conducting research in these areas to maintain dedicated cybersecurity and insider threat practices to prevent surreptitious review or theft of Covid-19-related material."
On Monday US media reported that the FBI was poised to release the warning about vaccine-research hacking.
Asked about the coming report, President Donald Trump replied: "What else is new with China? What else is new? Tell me. I'm not happy with China."
"We're watching it very closely," he added.
In Beijing on Monday, Foreign Affairs ministry spokesman Zhao Lijian rejected the allegation, saying China firmly opposes all cyber attacks.
"We are leading the world in Covid-19 treatment and vaccine research. It is immoral to target China with rumors and slanders in the absence of any evidence," Zhao said.
The warning comes as dozens of companies, institutes and countries around the world are racing to develop vaccines to halt the spread of the coronavirus, which has killed at least 292,000 worldwide.
Many more groups are researching treatments for infected patients. Currently there is no proven treatment.
The warning adds to a series of alerts and reports accusing government-backed hackers in Iran, North Korea, Russia and China of malicious activity related to the coronavirus pandemic, from pumping out false news to targeting workers and scientists.