RIO DE JANEIRO, Feb 26 (Reuters) - Brazil's biomedical institute Fiocruz has begun talks with AstraZeneca Plc over alternative COVID-19 vaccine sources in case of possible issues surrounding the local production of the shot, a director told Reuters on Friday.

Maurício Zuma, who heads the Fiocruz unit that produces vaccines, said it was still aiming to produce 110 million doses in the second half of the year, but that the complexity of the production and regulatory process in Brazil could stifle those plans.

As a result, he said it was exploring alternatives such as importing more active ingredients or ready doses.

The AstraZeneca shot was supposed to be the central pillar of Brazil's vaccination campaign, starting with imports and later moving to domestic production, but its rollout has been hit by snags.

"To produce the vaccine here is a whole process," he said. "We think we can have vaccines ready by the end of the third quarter, but whether we manage to deliver them will depend on regulatory questions."

Brazil's health regulator, Anvisa, has come under increasing criticism for being slow and for making onerous demands on vaccine producers.

"We know that we are going to have mishaps in a process that would usually take years,” Zuma added.

AstraZeneca has agreed to transfer the technology for the active ingredient in its COVID-19 vaccine to Fiocruz to allow for complete local production. But the agreement is yet to be signed due to the complexity of the deal, Zuma said. (Reporting by Rodrigo Viga Gaier in Rio de Janeiro Writing by Stephen Eisenhammer Editing by Matthew Lewis)