That condition seems to be fairly widespread right now already.
It's even encouraged under the moniker of "social distancing" (which itself is a telling misnomer; "physical distancing" would've been a much more appropriate and less jarring term but somehow that never stuck), even though there have been better alternatives (getting vaccinated, getting tested when meeting with a larger group of people, wearing high-quality masks) for quite some time now.
On the contrary - looks like a reasonable reaction to me. You know the risk for you is very high, so you protect yourself better against the infection. The best tool we have is avoiding the infection by increasing physical distance from the aerosols in the air exhaled by others.
If you're vaccinated and believe in vaccines, it's safer than ever in this pandemic to go out, especially if you avoid indoor areas. I am concerned about some people who haven't really left their homes since March 2020. I know some of such people, and they are really paranoid. They are vaccinated, but even if they are outdoors, they say that "everyone around is spitting on them". It's very unhealthy and the more they stay in isolation, the harder it is for them to convince themselves it's relatively safe to go outside.
On the other hand, there are people taking lots of unnecessary risks for no ones benefit. As a typical example, in the 12+ years I've been working at our research institute, nobody has ever organized an institute-wide joint lunch and nobody ever expressed any interest in it. On the contrary, many colleagues hate these kinds of events. But now that everyone is vaccinated (or at least assumed to be, nobody checks it), they have organized a 4 hour indoor meeting plus a joint lunch that you can hardly avoid. Nevermind perhaps waiting another year for organizing this. It has to be now to bolster team spirit, etc.
The people who do this think they're geniuses, and literally say things like "we should push people to go to international conference again instead of giving Zoom talks", and so on.
In reality, everybody just projects their own preferences and fears onto others. The people pushing for hitherto unknown social events are extraverts, the people who prefer to stay home and give Zoom talks are introverts.
The bottomline is that there is nothing wrong with being an introvert and avoiding large crowds is quite reasonable even when you're fully vaccinated. (Less so if you recently got a booster shot, but e.g. in our country it will take a while until every adult has received one.) Infection numbers in our country are going up rapidly, with an R-value close to 2. Then, close to Christmas when measures have to be announced, everybody will act surprised again, of course.
Looks like a psychiatric condition that needs a separate treatment.