A push by Democratic leaders to ensure the availability of low-cost vaccines could complicate negotiations on an emergency funding bill to combat the deadly disease caused by a coronavirus.

There is no vaccine yet to combat the COVID-19 disease that has spread around the globe from China. But lawmakers are eager to ensure that any future vaccine doesn’t become subject to price gouging that would deny people access to it.

House Speaker Nancy Pelosi and Senate Minority Leader Charles E. Schumer issued a statement Thursday saying any bill must include a guarantee that “vaccines are affordable and available to all that need it.”

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Senate Appropriations Chairman Richard C. Shelby, R-Ala., expressed general support for the idea Thursday: “I think that would be a worthy goal to make it affordable.” But other Republicans involved in pharmaceutical pricing issues said the coronavirus supplemental funding bill wasn’t the place to legislate on the matter.