Viruses don’t get eradicated.
Polio was re-defined overnight to reduce it by 75%.
Most virus mortality rates fell by 90% or more before the respective vaccines were even introduced. Why? Public sanitation, clean water, and improved nutrition. Nutrition can still eradicate illness from viruses. None other than the WHO recommends a mega dose of Vitamin A for measles in poor countries. Scarlet fever fell like all the other “vaccine-preventable” diseases with no vaccine. Typhoid IIRC fell similarly with minimal vaccination.
So far, one human virus, smallpox, has been eradicated through inoculations. In addition, one other virus, rinderpest, has also been eradicated through inoculations, but it only affected cattle, buffalo, deer, and several other species of two hoofed animals (even toed ungulates).
Most viruses evolve over time to become more contagious but less virulent. A virulent virus cannot spread efficiently, because it kills off its victims before they can pass it on. So, the less virulent a strain becomes, the more successful it is in spreading and reproducing.
Some human viruses have evolved to become very contagious, but not very virulent. These viruses can infect you repeatedly because you only get limited, short-term immunity from being infected (e.g., the common cold and influenza). Some human viruses are both contagious and virulent, but can only infect you once. If you survive, you get lifetime immunity (e.g., smallpox, polio, chicken pox, measles and mumps). Some viruses are virulent, but not very contagious, and provide no immunity (even short term), so if you become infected you are infected for life (e.g., HIV). These viruses have not evolved to become more contagious and less virulent, because once someone is infected it generally takes years to kill them and they can infect others before they have any symptoms up.
Smallpox was both contagious and virulent, but if you caught it and survived then you gained lifetime immunity. It has been around since at least the 1600s (and maybe as early as 1500 BC). It did not begin to disappear until inoculations began, initially with the variola minor virus, then with cowpox, and finally with the vaccinia virus, all genetically similar enough to smallpox to give smallpox immunity. Worldwide inoculations began in the 1700s. Smallpox was eradicated in the U.S. by 1950 and worldwide (including third world countries that still lack public sanitation, clean water, and improved nutrition) in the 1970s.
Polio, measles, mumps and chicken pox all also fall under the category of viruses that are both contagious and virulent, but that give lifetime immunity. These are the only types of viruses that have been successfully vaccinated against. After 75 years of inoculations, polio was almost eradicated (including in third world countries with no public sanitation, clean water, or improved nutrition), but cases still keep popping up in the wild in Afghanistan. With the Taliban back in control, the chances of eradicating it there are now next to zero. It will likely spread from there with refugees. I am surprised it has not yet spread back to the U.S. with Biden's open borders.
The flu vaccine can give short-term immunity, but only if you get vaccinated for the same strain that happens to be circulating that year. Since the flu vaccines must be formulated and manufactured in advance of flu season, it is hit or miss whether they will correctly guess which strains to vaccinate against. At best, the flu vaccine may reduce your chances of getting the flu in a particular year by 25-50%. In a bad year, it may reduce your chances of getting the flu by 10% or not at all.
Absent some great and unexpected breakthrough in medical science, COVID, the flu, and the common cold will never be eradicated through vaccinations, because getting them once does not give lifetime immunity, just short-term immunity. The cold and flu evolved that way. COVID was most likely engineered that way. I personally have had COVID twice, once in 2020 and again in 2022. I did not get vaccinated, but nearly everyone I know who did has subsequently either gotten COVID or died.