WASHINGTON (AP) — The government’s top infectious disease expert has told a House committee he believes “it will be when and not if” there will be a COVID-19 vaccine. Dr. Anthony Fauci also says he remains “cautiously optimistic” that some will be ready at the end of the year. He has returned to Capitol Hill at a fraught moment in the nation’s pandemic response, with coronavirus cases rising in about half the states and political polarization competing for attention with public health recommendations. Fauci was testifying along with the heads of the Centers for Disease Control and Prevention, the Food and Drug Administration and a top official at the Department of Health and Human Services.