A flurry of scientific gatherings and panels across federal science agencies were canceled on Wednesday, at a time of heightened sensitivity about how the Trump administration will shift the agencies’ policies and day-to-day affairs.

Several meetings of National Institutes of Health study sections, which review applications for fellowships and grants, were canceled without being rescheduled, according to agency notices reviewed by STAT. A Feb. 20-21 meeting of the National Vaccine Advisory Committee, a panel that advises the leadership of the Department of Health and Human Services on vaccine policy, was also canceled. So was a meeting of the Presidential Advisory Council for Combating Antibiotic-Resistant Bacteria that was scheduled for Jan. 28 and 29.

The Trump administration has instructed federal health agencies to pause all external communications, such as health advisories, weekly scientific reports, updates to websites and social media posts, according to nearly a dozen current and former officials and other people familiar with the matter.

The instructions were delivered Tuesday to staff at agencies inside the Department of Health and Human Services, including the Food and Drug Administration, the Centers for Disease Control and Prevention and the National Institutes of Health, one day after the new administration took office, according to the people with knowledge, who spoke on the condition of anonymity to describe private conversations. Some of them acknowledged that they expected some review during a presidential transition but said they were confused by the pause’s scope and indeterminate length.

The health agencies are charged with making decisions that touch the lives of every American and are the source of crucial information to health-care providers and organizations across the country.