Brazil will vaccinate an entire city's adult population to test the effect on Covid-19 infection rate

Serrana, Sao Paulo state, Brazil, Wednesday, Feb. 17, 2021.

(CNN)Brazil's Butantan Institute kicked off a campaign on Wednesday to vaccinate all of the adult population of a city to see if it's possible to reduce the number of cases.

The study will involve the city of Serrana, in the southeastern State of Sao Paulo, the research institute said
"The entire adult population, estimated at 30,000 people, will be immunized in three months, in an unprecedented action," the Butantan Institute wrote via Twitter on Wednesday.
The idea to vaccinate the largest number of people will allow researchers to "follow the evolution of the epidemic. It has technical aspects that will make it possible to make calculations, make projections and calculate whether the vaccine is capable of reducing the transmission of the virus, " said Dimas Tadeu Covas, the director of the institute.
    The city of Serrana, with a population of approximately 45,000, has been divided in four color-coded regions. All people over 18 will be administered a Coronavac vaccine with the exception of pregnant or breastfeeding women and those with serious illnesses, according to the Butantan Institute.
    Residents line up to receive the Coronavac vaccine against COVID-19, in Serrana, about 323 km from Sao Paulo, Brazil, on February 17, 2021.
    "Based on what we are going to learn here, we will be able to tell the rest of the world what the actual effect of the vaccination against Covid-19 is," Ricardo Palacios, director of clinical studies at Butantan, said.
    Brazil has been hard-hit by the pandemic since it began, and is nearing a total of 10 million Covid-19 cases. The country currently has the most coronavirus related deaths in the world after the US -- 242,090 according Johns Hopkins University -- and ranks third in the world for cases.
      There are rays of hope, Pan American Health Organization Director Dr. Carissa Etienne said on Wednesday. "After many weeks of increases in Covid cases and deaths, we are starting to see improving trends in some of the more heavily affected countries, including the US and Brazil," she said during a weekly online briefing.
      She warned, though, that those trends are "cause for hope, but not for celebration."