In fact, everything is simple. Many people are against vaccines for several reasons. In many countries, children are vaccinated almost immediately after birth. Many vaccines contain mercury, aluminum, and other substances that are toxic to humans (study the composition of the vaccines). Opponents of vaccination are not against vaccination in adulthood (or at least after 10-15 years) if it is necessary at the moment, they just do not want to worsen the immunity of their children at birth (since this will affect their whole lives). And this is rational. In addition, antibodies to many viruses are transmitted from mother to child in the womb (so it makes no sense to be vaccinated against them again).
No need to go to extremes, and during some kind of strong epidemic - you can and should be vaccinated. But it is also important to study all the available information from various sources on the Internet.