BRASILIA, Oct 29 (Reuters) - Brazil"s health regulator Anvisa said on Friday that all five of its directors have received death threats over possible approval by the agency of COVID-19 vaccinations for children aged between five and 11 years old. In a statement, Anvisa said it had reported the emailed threats to the police and prosecutors. It said the messages, which were sent on Thursday morning, threatened the lives of the directors if the agency approved vaccinations for that age group. Schools in the state of Parana were also threatened, the statement said. The threats came after Pfizer (PFE.N) said on Wednesday it would seek approval from Anvisa for its vaccine to be used on children between 5 and 11 years old. An advisory committee of the U.S. Food and Drug Administration (FDA) has recommended the use of the Pfizer shot for that age group, but with a lower dose. Brazil has one of the highest vaccination approval rates in the world and has, after a slow start, made progress in ramping up COVID-19 vaccinations. However, a nascent group of anti-vaxxers has grown in recent years, buoyed in part by President Jair Bolsonaro, who has refused to be vaccinated against the coronavirus. COVID-19 has killed over 600,000 people in Brazil, the second highest death toll in the world behind only the United States.