One way to stop an epidemic (even of pandemic proportions) is through vaccinations which increase immunity within the population and prevent viruses from spreading. We call that collective protection, “herd immunity.” Depending on how infectious a virus or disease is, herd immunity needs a greater or lesser proportion of the population to be vaccinated. For example, to achieve herd immunity for covid, we need to vaccinate about 70% of the population.

When we don’t achieve herd immunity, new mutations of viruses develop to get those blockers like vaccination. When you hear about “variants,” those are the mutations that have developed once humans begin fending off the virus. Often those variants are more infectious than the original strain of a virus. That is why it is important to get as much of the population vaccinated as quickly as possible.