As the Daily Mail reports, "They unearthed allegations of 'political interference' in scientific reports, raising fears that research was tampered with," and that "neither agency had a system in place for reporting allegations of political interference. It also said they had failed to train staff how to spot and report this."

The report defined 'political' interference as that which seeks to 'undermine impartiality... and professional judgement.' They set up an anonymous whistleblower hotline for 60 days which employees could call to report instances, and which received 'a few calls.'

A few respondents from CDC and FDA stated they felt that the potential political interference they observed resulted in the alteration or suppression of scientific findings. Some of these respondents believed that this potential political interference may have resulted in the politically motivated alteration of public health guidance or delayed publication of COVID-19-related scientific findings. -GAO

The whistleblowers say they didn't speak out earlier out of fear of retaliation - and didn't know how to report issues to higher-ups.