Vaccine Trial Raises Hopes, But Distribution Will Challenge States

States have worked vigorously for months on their COVID-19 vaccine plans but still face a long list of substantial uncertainties, even as hopes rise that the first vaccines could receive federal approval before the end of the year.

Despite the unknowns and the enormity of the task ahead — vaccinating a population of 330 million — state public health officials feel more confident in working with the federal government on vaccines than other matters such as testing, contact tracing and the production and distribution of medical supplies. On Monday, President-elect...