TOPEKA, Kan. (AP) — Four nurses at a rural health department in Kansas are refusing to administer any COVID-19 vaccines, citing the fast development and production of the shots.

The Kansas City Star reports that none of the Coffey County nurses, including the public health administrator, feel “comfortable” administering a vaccine that has gone through a speedy testing process with new technology.

Studies involving tens of thousands of people found that the two vaccines that have been authorized for emergency use in the U.S. are nearly 95% effective at preventing COVID-19 illness. So far, the vaccines have been given to more than 10 million people in the U.S.