The primary advantage of vaccinated people over non-vaccinated people is their protection against Covid-19 disease; especially its serious course, or eventually hospitalization or death in association with Covid-19 disease. Despite the fact that there are cases of getting infected even in properly vaccinated persons, the probability of getting infected or having a serious course of the disease is significantly lower than in case of non-vaccinated people. Administration of a booster dose significantly lowers the probability of eventual infection or serious course, and secures a higher health protection in people at risk. Some studies show that after the booster dose application, the level of protective antibody increases five or even eleven times than after the second dose administration. What is more, this immunity boosting happens really fast, usually within days. After the first dose, it takes up to three weeks before the body reacts to vaccination by making antibodies. However, the antibody response alone is not sufficient for the assessment of vaccines effectiveness and for that reason it is needed to wait for clinical studies’ results. Since the duration of protection after vaccination differs with each person, none of us can predict with certainty for how long he or she is protected. That is why, as soon as it is possible for certain group of people, the maximum we can do against Covid-10 disease is to get revaccinated.