Science has not yet sufficiently studied what level of antibodies in the blood is necessary for optimal protection against the human papillomavirus. In early clinical studies, it was observed that women’s blood levels of antibodies continued to rise after each dose administered. But over time, antibody levels inevitably dropped as soon as the vaccine was stopped, but the initial high concentration of antibodies provides the best protection against HPV for years or even decades.
Over time, scientists were able to prove that three doses are not necessary and that vaccination can be carried out every year in small doses.