it doesn't have to have non-zero benefit vs. variants, it just has to have non-zero benefit overall to outweigh the negligible cost in the net cost/benefit calculus
Keep in mind this discussion thread is about people who have already contracted Covid and recovered.
The benefits:
Unknown increase in immunity against alpha strain
Unknown increase in immunity against variant strains
...
The Costs:
Chance of currently known adverse effects
Chance of unknown adverse effects specific to vaccination of people with prior immunity.
Some recent data [1] suggests that those with prior covid infection 13X lower chances or reinfection with delta than those with 2 vaccine doses. If this is accurate, it begs the question of how much benefit is gained by vaccination on top of existing immunity in comparison to to the rare but known side effects.
Im sorry, but that is missing the point.Any benefit doesn't equal cost/benefit.
For some with naturally acquired immunity, Both costs and benefits are amazingly small!
If you are a healthy 18 year old (infection fatality 1/100,000)[1] w/o vaccine, plus have previously acquired immunity 13X better[2] than a vaccine 90+% effective, you are talking about about 1/ 10s of millions of chance of death or severe complications IF you are infected. This easily puts it in competition with the more serious vaccine complications.
Looking at just two aspects for this hypothetical individual, you could weigh
1/10 million chance of death with no booster vaccine shot VS 17/100,000 chance of bells palsy[3] and a 60% chance of fever, chills and headache.
A analsys from the previously linked lancet study had a muck larger sample ~500k, but different collection methods and found smaller but nonzero results
>The age-standardised difference for the incidence compared with the background population was 41·5 (95% CI 11·7 to 71·4) for CoronaVac and 17·0 (−6·6 to 40·6) for BNT162b2, equivalent to an additional 4·8 cases per 100 000 people vaccinated for CoronaVac and 2·0 cases per 100 000 people vaccinated for BNT162b2.
Most if not all the vaccine trials saw small increases <1% in serious adverse events in the treatment arm
