It doesn't reduce it enough to provide herd immunity, meaning the virus will continue to propagate until every one has been exposed. See Iceland's experience:

It doesn't reduce it enough to provide herd immunity, meaning the virus will continue to propagate until every one has been exposed. See Iceland's experience: https://twitter.com/eliaseythorsson/status/1424011542195023878?s=20 https://twitter.com/eliaseythorsson/status/14240115421950238... The Oxford Vaccine Group says herd immunity through vaccination is infeasible now: https://www.theguardian.com/world/2021/aug/10/delta-variant-renders-herd-immunity-from-covid-mythical https://www.theguardian.com/world/2021/aug/10/delta-variant-...