Also Read | How plant meat is coming of age in India"Even as vaccines start protecting the most vulnerable, we're not going to achieve any levels of population immunity or herd immunity in 2021," Swaminathan said. "Even if it happens in a couple of pockets, in a few countries, it's not going to protect people across the world."Scientists typically estimate that a vaccination rate of about 70% is needed for herd immunity, where entire populations are protected against a disease.