I spend much time prompting those who have had bad reactions to put in Yellow Card reports. Quite a number have done so. It is, of course, vitally important that this is done.Oyster, there must be a certain fraction of the population who cannot for valid medical reasons be vaccinated. However ,I have no idea what those conditions are, and why they cannot be vaccinated. However it must be very possible for the appropriate authorities to flag up this cohort and list it in the official data. Unless they have been informed by the competent medical consultant, they are self diagnosing, and are actually in the egotist grouping.
Imagine you have a disorder, and you are in contact with many who have the same disorder. Initially, all are willing to receive the vaccine (whether the initial doses or a "booster") and they start to do so.
As time passes, maybe 80% of those who have had a vaccine report extremely similar and significantly nasty adverse reactions. These worsen the people's original, known disorder and make the medication taken for that change in effect. (Flip-flopping between under- and over-dosed.)
Everything about this is new, so it is impossible for the medical people to confidently reassure people. (Unless they just speak the words without the supporting medicine and science.) They might find analogous cases across other disorders, they might start looking further. They might do everything right. But people are people. At some point they will bail out. Very likely before the establishment has collected the necessary information and done the required analysis.
Remember, these same people have, by and large, already gone through the original vaccinations and supported each other in doing so. They are not intrinsically vaccine averse. Nor "it can't happen to me" people - why, if they had thought that earlier in their lives, they have learned the hard way they are not immune to anything through getting their existing disorder. They desperately do not want to get Covid.