American researchers studied a large group of female students for at least five years. The study included female students who started having sexual contact within the 6 months prior to being included in the study and it focused on infection percentages over time (the uterine cervix was tested for HPV DNA every 6 months). It was found that, within the first two years, 60% of the students were infected by one or more types of HPV, and within five years 80% of them had been infected. The infection percentages were proportional to the reported number of sexual partners.
It is self-evident that the restriction of the number of sexual partners reduces the risk of infection.