BRASILIA—Brazilian health regulator Anvisa has canceled a request for emergency use authorization for the COVID-19 vaccine developed by China’s CanSino Biologics Inc. after the laboratory cut ties with its Brazilian representative. The move follows a wave of scrutiny in Brazil of vaccine contracts negotiated by intermediaries, a common local practice. Federal prosecutors and Senate investigators are probing a deal for an Indian vaccine, with one senator accusing President Jair Bolsonaro on Monday of turning a blind eye to alleged irregularities. The president and companies involved in those talks have denied any wrongdoing. CanSino and its former Brazilian representative, Belcher Pharmaceuticals, Inc., did not immediately respond to emails requesting comment on the end of their relationship. Brazil’s Health Ministry signed a letter of intent on June 4 with Belcher to buy 60 million doses of CanSino’s single-shot vaccine for delivery in the second half of this year, according to a document …