by Elena Riboldi (Agenzia Zoe)
Key messages
- The prevalence of infection with high-risk oncogenic strains of human papillomavirus (HPV) is much higher in girls who undergo specific vaccination after the onset of sexual activity and not before.
- It is advisable to follow the vaccination schedule that recommends vaccination at an age that is highly likely prior to the first sexual experiences.
Vaccination against the human papillomavirus plays a crucial role in the fight against cervical cancer and other cancers affecting both sexes.Getting vaccinated is important, but it is very important to do it at the right time. A study by the National Cancer Institute shows that among vaccinated girls, infections from the strains at highest oncogenic risk (HPV-16/18) are 82% less frequent in the group of girls who received the vaccine before the onset of sexual activity. Adhering to the recommendations, which fix vaccination by the age of twelve, offers greater guarantees of obtaining maximum protection.
The researchers analyzed data collected from 2011 to 2018 by the National Health and Nutrition Examination Survey (NHANES), a program aimed at assessing the health status of adults and children in the United States. This program, which involves a representative sample of the population every two years, combines interviews, visits and medical examinations. Among the aspects considered is that of sexuality, with questions that include age at first intercourse, number of partners and history related to sexually transmitted diseases; the survey participants are then subjected to the HPV test.
The analysis included the female population who were between 9 and 26 years old in 2006, the year of introduction of HPV vaccination, eligible for routine vaccination (9-12 years) or for catch-up vaccination (13-26 years).We compared the prevalence of HPV-16/18 infection in those who had been vaccinated before or after becoming sexually active.
Among survey participants (n=4,727), only 38% had been vaccinated against HPV. In addition, only 21% (95%CI 14%-28%) had received the vaccine by age 12 as recommended by the Advisory Committee on Immunization Practices (ACIP); The mean age at first dose was 14.5 years. 42% of women had been vaccinated after the onset of sexual activity.
The prevalence of cervical infection was 6% (95%CI 4%-7%) in the unvaccinated group, 3% (1%-6%) in the vaccinated group after the onset of sexual activity, and less than 1% (<1%-1%) in the vaccinated group before that event. Compared to the unvaccinated group, the prevalence of infection was reduced by 89% in the vaccinated group before, but only by 41% in the vaccinated group after the first sexual intercourse.
«It is estimated that vaccination by age 12 prevents most cervical cancers caused by HPV-16/18, but this benefit is reduced by a quarter if the age at vaccination rises to 16 years – report the authors of the study, published in the journal JAMA Network Open – To ensure maximum effectiveness of vaccination, pediatricians must insist on the importance of punctuality in HPV vaccination».
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