No medicine or medical procedure has a 100% guaranteed exactly identical result for everyone...
(as humans are odd-bods and there are always some obscure anomalies)..
No medicine or medical procedure is a 100% guaranteed cure claiming that you will never ever be able to catch something again at a later date..
Pre-lockdown, when travelling abroad to numerous exotic locations was allowed, an abundance of vaccinations were administered every year..
with all sorts of various possible side-effects and/or guidance of things to avoid following the treatment..
Covid-19 is one of a variation of Coronaviruses that have been known about and investigated for many years..
It is not a completely new, unknown quantity, that has had to be started from scratch last year to evaluate possible solutions / vaccines.
https://en.wikipedia.org/wiki/Coronavirus
Right from day 1.. the fundamental guidance has been that the majority of people who are infected with Covid-19 will have relatively mild symptoms..
and probably 10% or less will have serious symptoms possibly needing medical help..
Hence the advice to isolate for 2-weeks AND ensure basic hygiene, hand washing etc as a major defence!
(We are convinced our youngest, in his 20's had Covid back in Jan 2019..
He lives & works in Portsmouth and had major flu like symptoms, horrendous cough, pretty much bed ridden for approx 5 or 6 days, since then all OK again!).
BUT..
Just like the common cold the volume of people who are infected can be very very very large..
and it can be easy to catch if kept in close proximity to others who are infected..
So even a minority who have more serious symptoms, from a very very vary large group,
(often compounded with other underlying medical issues, age, diet, weight etc..),
can cause serious congestion at hospital emergency departments..
Which is the bottom line problem in all this...
[ Saving Hospitals Not People. ]
If you did get really ill..
there may not be "room at the Inn" to treat you!
Bit like why you take vaccines before going abroad, as there may not be room/knowledge/resources in a distant foreign country like you have back home..
You just need to think of it as taking a jab before popping off to to remote island where they have no NHS to patch you back up if you get ill..
My dad and mother-in-law have both had their first jab, and neither have grown horns or losing their hair....!
Guinness