Most of us old enough to be participating in the 50+ forum had multiple doses of some vaccines, but probably have forgotten. That wasn't unusual in the 1950s-'60s, and still common for some immunization against certain diseases, notably polio, diphtheria, pertussis and tetanus. If our military duty or jobs take us overseas we'll usually get a number of other vaccinations. By the time I finished boot camp in 1976 I'd had at least a dozen injections, including for plague, since rotation for my rating usually included a stint in Okinawa, Japan, other parts of Asia, Africa, etc.
Earlier this year my apartment was flooded (elderly neighbors upstairs trying to flush disposable diapers and sanitary wipes, which don't disintegrate in water and tend to hang up on the insides of the old cast iron pipes in this building). Unfortunately one of my family photo and keepsake albums got wet, including my childhood vaccination record. The red ink pen used for some entries blurred, but I could see that, before first grade, I'd received four DPT injections and five treatments for polio (at least one of which was the sugar cube, which I remember). I do remember receiving more than one each, but not four or five.
In some cases additional boosters for some diseases are advised for adults at risk of exposure. The vast majority of Americans accepted this as normal practice, at least until the anti-vax hysteria infected the public psyche in the 1990s. That includes some of my relatives, who bought into the paranoid conspiracy theories and notions that vaccines are secret weapons designed by (X) to do (something something something) to the population. This has been inflamed by misuse of the VAERS database by flooding it with flawed data or outright disinformation, misleading some people -- including a distant relative, who believes the COVD vaccine caused a 10,000% spike in cancer. Never mind that this person can't interpret data, flawed or otherwise, and that isn't what the VAERS data shows anyway.
A somewhat less flawed interpretation making the rounds is that the COVD vaccines caused a spike in myocarditis, especially among young men. But the data doesn't support that and so far the instances of myocarditis in that demographic -- already miniscule -- make up a relatively small sampling group, so that it's almost impossible to determine a particular cause for any tiny spike in excess over the usual instances. Rarely, if ever, mentioned is the risky behavior of young men that contributes to a higher risk for myocarditis, ranging from inadequate rest, poor diet, consumption of alcohol and drugs, smoking of all kinds of substances, disregard for personal and public hygiene and communicable disease, combined with physical exertion without regard to need for proper training, rest and recovery.
Even before the COVID anti-vax hysteria I was already seeing misinformed anti-vax posts online regarding flu vaccines. Some folks didn't understand that the flu virus mutates, and the vaccines are usually educated guesswork but almost always safer than getting the flu, particularly for vulnerable people.
As with many viruses that use the respiratory system as the entry point, the SARS-CoV-2 virus has mutated to the point that some of the earliest vaccines and certain anti-viral treatments are no longer effective. But the vaccines are modified, along with anti-virals. So we can expect the boosters to be recommended every six months or so, perhaps more often to the most vulnerable people. Nothing unusual about that.
And as with other viruses, it tended to mutate toward being less deadly but more contagious. As with research into the 2004 SARS outbreak, research now indicates the respiratory system is merely the entry point, but COVID can cause adverse effects throughout the body, including the brain, nervous system and cardiovascular system.