The government hopes the nationwide testing will speed up a recovery from the latest wave of the infections, make it possible for students to return to school in February, help the health system and ease restrictions that harm the economy. RIO DE JANEIRO — Brazil’s health regulator on Sunday approved the urgent use of coronavirus vaccines made by Sinovac and AstraZeneca, enabling Latin America’s largest nation to begin an immunization program that’s been subject to months of delay and political disputes. The process to present and approve the COVID-19 vaccines was fraught with conflict, as allies of President Jair Bolsonaro sought to cast doubt on the efficacy of the Sinovac shot backed by his political rival, Sao Paulo state’s Gov.