An interesting experiment is about to be carried out with the British as the control group.
The only thing we know for certain about C19 is we don't know anything for certain. The EU recognise that fact and are playing for time. The UK, on the other hand, is pretending to have a sciencey fix based on some adolescent game theory nerdgasm. Herd immunity can be conferred by both vaccine and disease. But there's a difference between vaccine and disease that seems too subtle for Whitehall to grasp.
The UK is planning for 60% of its population - forty million people - to contract C19. The gamble is that this won't overwhelm the health system. How? Because the government has told the virus not to infect people who might get ill.
In China, healthcare workers were at greater risk than the general population because of elevated exposure. The UK has told the virus not to infect doctors.
The big risk with RNA viruses is mutation: we could develop a vaccine this year that's useless next. Obviously, the larger the infected population, the higher the viral mutation rate. China and the EU are responding by locking down. The UK has told the virus not to mutate.
When declaring a pandemic, the WHO director-general said, “The idea that countries should shift from containment to mitigation is wrong and dangerous.”