The journal of immunology estimates that based on their entire knowledge and experience of other similar infectious diseases, we should assume at least a year of immunity from covid.

But we're getting to the point in the next 6 months about 10% of Brits will have had it a year ago.

Then what happens? It's entirely possible there could be mass reinfection, as it's simply too hard to predict how strong immunity will be at this point.

So to be honest it's a risky strategy to go for herd immunity now given that it means in 2 or 3 months well have thousands of deaths per day and then in 6 months a huge proportion of those immune could lose their immunity and it all starts again.