”Herd immunity” - sufficiently many people within the population with immunity to the disease that an infected individual will not cause spread within the general population. Typically assessed to require a high percentage immune, but numbers by definition not known now.
”Letting it rip” - a policy at current levels of infection of not actively trying to suppress incidence through measures like social distancing or restrictions on human interactions
Yes, one person won't cause spread within the general population, which is to say a drop in the underlying rate of r to 1 or less. We are going to get there in the end one way or the other. The options are:
- slowly passing the disease round most people, while probably failing to shield the vulnerable because it's all far too long, and trashing the economy to boot
- relatively quickly passing the disease round most people, shielding the vulnerable as well as possible, and keeping life intact
- permanently changing our lifestyles to a point where r<1 without any gain in immunity
Or
- go as slowly as possible while we wait for a vaccine to hopefully gain a bit more shielding for the vulnerable, whilst killing the economy, cancer patients and people who can't cope
The vaccine is only going to go to the over 50s, so any notion it's going to help with long Covid is a simple lie. There is no benefit to the non-vulnerable in any of the slower courses of action at all. For the vulnerable it might help, but only if the vaccine arrives fast, works and we get really lucky, otherwise most of them are going to get it before the vaccine offers them a level of shielding anyway.
Contrary to some of the wild claims of locktivists, including those who should know better such as Devi Shridhar, naturally acquired herd immunity has been vital in a range of diseases. That includes measles - a significantly more deadly disease than Covid which used to kill loads of people, but a fraction of those who were vulnerable, simply because it bubbled around without ever becoming an endemic disease.
Herd immunity is basically the end-game of all the strategies, and the fact that it has turned into a term of abuse for the only strategy that will get us there without destroying the country is a real shame