As long as vaccines continue to prevent vast majority of severe cases that require hospitalisations then there is no reason to lock down once everyone who wishes to get vaccinated can. IMO that should mean over 30's and anyone with any underlying condition who is also younger. The virus is extremely unlikely to lead to hospitalisation or any long term effects once you start to get to under 30's. The only people who are dying or getting extremely sick in the young age bracket are those with underlying issues who should be vaccinated anyway. The UK is the first real test of fighting a new strain with a high % of their population vaccinated and its showing that they were pretty damn well.. Not perfect (in fact half of the recorded deaths were fully vaccinated) however the number is way way lower than previous waves when cases were at the same level.