The Department of Justice announced last week that two Chinese hackers have been indicted on charges of trying to hack COVID-19 vaccine research in the U.S.

While not naming specific companies, the indictment accuses the hackers of probing a Maryland biotech firm between Jan. 25-27. The company had announced that it was researching a COVID-19 vaccine a week earlier.

The hackers are also accused of searching for vulnerabilities in a Massachusetts biotech “publicly known to be researching a COVID-19 vaccine” on Jan. 27. Moderna, based in Massachusetts, is expected to begin phase 3 testing of its vaccine this week.

The hackers also targeted a California biotech on Feb. 1 that had announced a day earlier that it was researching antivirals for COVID-19. Gilead Sciences, based in California, announced it was investigating its antiviral remdesivir for COVID-19 treatment on Jan. 31.

The charges unsealed last week come one week after the UK’s National Cyber Security Center (NCSC) accused Russian hacker group APT129 of engaging in cyberattacks this year against U.S., UK and Canadian organizations involved in COVID-19 vaccine research and development. NCSC said the group was “almost certainly part of the Russian intelligence services.”

Neither Gilead nor Moderna responded to requests for comment about the indictment of the Chinese hackers.