Microbiologists work in a foodborne disease outbreak lab at the federal Centers for Disease Control and Prevention in Atlanta.

WASHINGTON — Republicans are intent on repealing a public health fund created by the Affordable Care Act — but with President Trump also pursuing a dramatic reduction in domestic spending, lawmakers admit they don’t know if they could make up the losses at one of the nation’s most critical health agencies.

The latest version of the GOP health care bill would end the law’s Prevention and Public Health Fund, which provides nearly $1 billion annually, in 2019. Those dollars have become an integral part of the Centers for Disease Control and Prevention’s budget, accounting for one-eighth of its funding and providing more than $300 million for immunizations alone.