Ok so my friends reply makes sense
Ok what we know:
* if you've had covid once you can get it again as little as 4 months later, perhaps less. The shorter the time between infections, the more likely it is to be milder second time, in fact very likely to be asymptomatic, which is great for the person involved and terrible for infection control as they can still be infectious i.e. a silent carrier.
* some of the vaccine strategies hope to achieve full immunity (i.e. can't get ill and can't carry) but others, and perhaps the ones which will be ready first, may only prevent you getting ill but you can still carry it.
* there's no hope of herd immunity unless you can get to a point where ~60% of people can't *carry* it, hence definitely not possible without a vaccine.