The Centers for Disease Control and Prevention is instructing states to sign so-called data use agreements that commit them for the first time to sharing personal information in existing registries with the federal government. Some states, such as New York, are pushing back, either refusing to sign or signing while refusing to share the information.

Gov. Andrew M. Cuomo of New York warned that the collection of personal data could dissuade undocumented people from participating in the vaccination program. He called it "another example of them trying to extort the State of New York to get information that they can use at the Department of Homeland Security and ICE that they'll use to deport people."

Administration officials say that the information will not be shared with other federal agencies and that it is needed for several reasons: to ensure that people who move across state lines receive their follow-up doses; to track adverse reactions and address safety issues; and to assess the effectiveness of the vaccine among different demographic groups.