There are reports floating around that the new corona virus, Covid-19, can be caught multiple times by the same person and each wave is more severe than the last.
If true, that does not bode well for a vaccine.
Some diseases, tetanus/lockjaw for instance, do not always render immunity to future episodes because such tiny amounts of the pathogen are required to produce the amounts of toxin needed to create the disorder. Furthermore, Clostridium tetani is an obligate anaerobe, it will not grow where there is good blood circulation. That tiny amount is not always enough to trigger a robust, durable immune response.
However, the vaccine ensures that enough bacterial seedcoats are inserted into the circulatory system where the immune system can get a good look at it.
The contention that patients are vulnerable to multiple waves of Covid-19 is puzzling. Let us hope that the appearance of multiple infections is really the virus lurking and manifesting in different organs rather than completely new infections.