Lootman wrote:Julian wrote:Also effectiveness against transmission?
Not a realistic criterion since obviously even someone vaccinated up the wazoo could breathe in a mouthful of virus and then immediately breathe it out all over someone else. The point of a vaccination is surely that:
1) Any virus in your body is neutralised more quickly, and so:
2) The amount of time you are infectious is thereby greatly reduced, and:
3) You won't get symptoms and so you won't be coughing and sneezing over others.
Effectiveness doesn't automatically imply 100% prevention, there are varying degrees of efficacy against all of the metrics that Mike mentioned.
Also, I'm not a virologist or have any sort of expertise in any appropriate area but I have heard more than one virologist on TV talking about the concept of "sterilising immunity" as the gold standard for vaccines which (if I understood it correctly) is when a vaccine is able to totally block a virus even getting into any of the hosts cells. Since viruses need to use apparatus within the hosts' cells to replicate (e.g. ribosomes to make the proteins for new viral particles) if they can't do that then breathe in a million virus particles and that's all your body ever gets, and as you say many of those are probably immediately breathed out again since that can't latch on to anything in the host.
In the case of a vaccine capable of sterilising immunity I assume that would break the transmission chain. I'm not sure how a virologist or epidemiologist would characterise your example of simply breathing in a lungful of air containing viral particles and breathing it out again. In that case the person involved hasn't given the viral particles the opportunity to replicate, i.e. grow in numbers, that person has simply redistributed what was in the air already so acting more like an air conditioner (without a Hepa or equivalent filter) or a contaminated surface rather than part of a human transmission chain.
Sadly of course none of the current SARS-CoV-2 vaccines, good as many are, are at the level of sterilising immunity.
- Julian