Covid-19 cases in the United States topped 22 million on Saturday. The US has recorded 22,132,397 cases with 372,428 fatalities.
India's Covid-19 tally reached 10,431,639 while the death toll rose to 150,798.
Brazil's Covid-19 death toll reached 202,631 on Saturday after 1,171 more patients died from the novel coronavirus during the past 24 hours, official data showed.
Brazil has the world's second-largest Covid-19 death toll, after the United States, and the third largest outbreak, after the United States and India.
A new study revealed that Covid-19 patients who recovered from the disease may have strong immunity from the coronavirus eight months after infection.
The study shows immune cells primed to fight the coronavirus should persist for a long time after someone is vaccinated or recovers from infection, said a report of MIT Technology Review.
The result is an encouraging sign that the authors interpret to mean immunity to the virus probably lasts for many years, and it should alleviate fears that the Covid-19 vaccine would require repeated booster shots to protect against the disease and finally get the pandemic under control.