According to the Guardian,

Marc Lipsitch, a professor of epidemiology at Harvard and co-author of the study, said: “Infections spread when there are two things: infected people and susceptible people. Unless there is some enormously larger amount of herd immunity than we’re aware of … the majority of the population is still susceptible.

“Predicting the end of the pandemic in the summer [of 2020] is not consistent with what we know about the spread of infections.”