[u801e]

Mass vaccination is the standard way to minimize the spread of viral infections. For example, there were routine outbreaks of varicella infections amongst children despite the fact more than 99.5% Of the adult population had natural immunity to it. After the vaccine became part of the standard schedule, outbreaks are virtually unheard of.

The same can happen with COVID-19 if the percentage of the population that's vaccinated is high enough. Of course, if that percentage drops below the herd immunity threshold, then outbreaks may occur. In fact, that happened several years ago with the measles virus because asubset of the population refused vaccination.

[bsaul]

the scenario you described is for vaccines that prevent infection. This is now obviously not the case with covid and 75% of the pop vaccinated, which still catch and transmit the disease enough to get the numbers we have now.

[u801e]

No vaccine has a 100% success rate in preventing infection. In fact, many of the standard vaccinations are not nearly as effective on an individual level as one may believe. At the population level, they are pretty effective because a high percentage of the population is vaccinated and/or has natural immunity.

Looking at the natural immunity scenario, one can consider the history of varicella. Prior to widespread vaccination, there were yearly outbreaks amongst children, despite the fact that more than 99% of the adult population had immunity due to prior infection. That is, despite the fact that the adult population was largely immune, there were still outbreaks among children.

Once the varicella vaccine became part of the standard vaccine schedule, those outbreaks essentially ceased. That doesn't mean that the virus isn't still being transmitted. It does mean that if enough people refuse getting the vaccine for their children, then there is a risk of another outbreak precisely because the percentage of people immune to the infection dipped below the herd immunity level.

Similarly, with COVID-19, if we can get the vaccination percentage up to more than 90 to 95% (or whatever percentage the data supports), then outbreaks will cease, but the virus will still be out there.