When is covid vaccine strongest in seniors? 2 weeks after the shot the strength of the booster wd be greatest?...and then gradually decline before the next shot. is there any evidence of when is strongest? shots are 6 mth apart? were not in usa?

'Greatest' strongest 'and other such terms do not define any vaccination. In general a vaccine starts producing antibodies against the disease in 48hrs and the affect is maintained till a gradual tapering off. The time of tapering off depends on the virus/ bacteria and the persons immune system. EG small px has a very long lasting immunity and some viral ones about 6months or so