e.g. the pox vaccine some people received 50 years ago still seems to protect against monkeypox now and the HPV vaccine also seems to provide long lasting protection ("at least 10 years, probably more").
The only coronavirus vaccine that I’m aware of prior to covid was one for dogs.
And almost every, single, time. C19 is behaving like a new C-class virus with some new symptoms such as a chesty cough and a risk of pneumonic like symptoms in those who have non perfect health. I.e. it's not been bioengineered to kill it be more or less contagious, or cause people to grow a 3rd arm.
"The Latin word "virus" isn't widely attested, and never in the plural. It seems to refer to something like a miasma - that is, a substance, that has no plural.
The English word Virus, refering to a particle of an infectious agent, should therefore be treated as an English word, of which the plural form is "viruses".
[Edit] There are singular nouns in Latin that end in "-us", which do have a plural form, but that plural form is spelled the same as the singular form. So it's possible that the plural of the Latin "virus" was "virus". But as far as I'm aware, it wasn't a countable noun.
Also, if we want "virus" to mean a particle, then it's inconvenient for the plural to also be "virus" - we'd like a notation for referring to multiple particles.
[Edit 2] It's worse, isn't it? We refer to the "Covid-19 virus", meaning the global population of that group of strains; the individual strains in the group might then also be referred to as a singular "virus", in the sense in which we might refer to urban air-pollution being caused by "the car".
I gave up using words like "stadia" and "referenda" many years ago. I'm afraid I'm very pedantic about language, but I now think those are a sort of back-Latin, and they sound pretentious. "Stadium" and "referendum" are English words now, and the way normal people pluralise them is correct.
Your "sed" suggestion is interesting, but there are many abused words that my inner pedant would have to put through the filter. Not all of them are HTML markup. So I envision a kind of "super-sed", that can auto-translate all of my linguistic experience, including text, speech, video, and even road-signs, and make everything nice for me.
Neat startup plan: world-changing idea, huge ambition, no detailed explanation of how it works, but hell; fake it till you make it.