According to a study published in the journal medRxiv , Manaus, a city in Brazil, may have developed herd immunity against the virus due to the unprecedented rate of coronavirus infection.

The city that comes under the area of the Amazon rainforest was ravaged by the coronavirus outbreak.

More than half the population seropositive

The study suggested that the coronavirus reached its peak in Manaus during March and April and the rate fell down in May and September.

Researchers found that in the peak, 44 per cent of the population were seropositive for the virus. This number was adjusted to 52 per cent after cases of false-negatives came to the picture.

Seroprevalence declined

The study noted that seroprevalence declined in July and August due to waning antibodies.

The study estimated after data adjustment that the final epidemic size was 66 per cent in terms of seroprevalence.

The authors of the study noted that government measures may have helped in controlling the pandemic, but the “unusually high infection rate suggests that herd immunity played a significant role in determining the size of the epidemic.”

Health experts, however, have warned that deliberately raising herd immunity can have dangerous implications.

Also read: Herd immunity to Covid unlikely, impractical: Study

Meanwhile, Brazil is the third-worst affected country by the novel coronavirus with over 49.5 lakh cases as of September 24. The country has also reported 1.38 lakh deaths, the second highest in the world, as per worldometer dashboard.