Most received the vaccine offered by Pfizer, and this week the drug maker said that presented an opportunity: Pfizer announced that it would fully vaccinate everyone in the city over the age of 12 so it can carry out a study of the safety and effectiveness of the vaccine.

The company will work with local health officials, a hospital, a university and Brazil’s national vaccination program to monitor the transmission of the coronavirus in a “real-life scenario” after the whole population has been vaccinated with the Pfizer-BioNTech serum, Pfizer said.

The study will follow participants for up to one year to investigate how long vaccine protection lasts against Covid-19 and new virus variants.

“Here we believe in science and we lament the almost 600,000 deaths from Covid-19 in Brazil,” Mayor Beto Lunitti of Toledo said in announcing the Pfizer study.

The study comes after the experimental inoculation of almost every adult in the southeastern Brazilian town of Serrana. That experiment was believed to be the first mass trial of its kind in which an entire town was vaccinated against the coronavirus before the rest of the country.

The experiment in Serrana was conducted over three months in winter and spring. Sinovac’s Covid-19 vaccine was put to the test in the town of 45,000. It was a resounding success, with steep drops in new cases, hospitalizations and deaths, at a time when the rest of Brazil was in the grip of the pandemic.