This study showed that the incidence of HPV infection, which occurred during both the first and second doses among male adolescents in most municipalities in the state of Minas Gerais, was considered very low (<50%) or low (≥50% to <80%). Among female adolescents, the highest percentages were adequate (≥80%) or low (≥50% to <80%).
In Brazil, the HPV vaccine faces challenges, such as changes in the target population and in the vaccination schedule over time, and it is currently offered free of charge in the SUS for individuals aged 9 to 14 years based on a scheme of two doses, with an application interval of six months(22).
Since their licensing in 2006, HPV vaccines have been progressively introduced in many countries. European countries started their vaccination schedule earlier in their immunization programs, and in some of them, HPV vaccination programs were successful from the beginning and maintained high vaccination coverage. However, in other regions, such as Japan, Ireland and Denmark, there has been a significant decrease in VC since the introduction of the vaccine(23).
In Brazil, coverage rates are not very different from those in these countries, and at the beginning of the vaccine introduction campaign, 87% of Brazilian municipalities reached the recommended target in the first dose in 2014, but only 32% of them reached the recommended target in the second dose(9,11). This scenario of falling global VC, including that of the HPV vaccine, has been worrying to health managers on a universal scale(24).
The introduction of a new vaccine to the population can contribute to vaccine hesitancy(25) and, consequently, interfere with VL. However, other factors, as highlighted by Beharry and collaborators(13), can also contribute to adolescents' VC. In this scenario, adolescents rarely attend health services and rarely engage in health promotion activities, both due to the characteristics of biopsychosocial development and because of the lay understanding that the age group has “good health” and would not benefit from medical consultations. routine(26, 27). Furthermore, many adolescents (and family members) are not aware of the need for vaccination in their age group(28); for example, the lack of health education at school, where adolescents spend a large part of their time, also contributes to a lack of this knowledge or greater care.
Another relevant factor for vaccinating adolescents is professionals, especially ESF professionals, as not everyone is prepared to address the idiosyncrasies of adolescence(27). Furthermore, not everyone encourages the updating of adolescents' vaccination schedules when they attend health care services(28). They also use the myth of the father or guardian's need to offer care/interventions, not guaranteeing the adolescent's rights.
Finally, it is known that there are intrinsic reasons for the organization of the health system and the social constructions that can impede the path of adolescents to primary care centers(27). This factor deserves much attention, especially in a country such as Brazil, where 61% of children and adolescents live in conditions of socioeconomic vulnerability.
The role of the COVID-19 pandemic in reducing VC in children and adolescents cannot be ignored(29-32). A study carried out with another immunobiological agent, exclusively for the adolescent population in Minas Gerais, showed that in 2020, the VC for this immunobiological agent was 52.28% for the first dose and 25.69% for the second dose(33).
Another finding of this study was that, in relation to males, for both the first and second doses, the higher the urbanization rate was, the lower the VC values were. For females, for area and number of families with a minimum wage, the coefficients indicate that the higher the values observed are, the lower the CV in the municipalities. For the variable population of the opposite sex and proportion of families served by the ESF, the higher the values observed were, the greater the VC was at the first dose.
In the U.S., a study on the association between HPV vaccination, income and type of health care (with health insurance and/or without) produced similar results. A study showed that adolescents from low-income families without health insurance were more likely to start the HPV vaccination process(34).
Work carried out in Brazil showed that HPV vaccine coverage increased in the population who lived only with their mother and had a higher level of education(35).
These findings emphasize that, in the absence of universal public policies, adolescents in a context of greater social vulnerability will have reduced access to vaccination and will be more subject to health problems, such as cervical cancer(35).
In this sense, the ESF, first named the Family Health Program (FHP), officially implemented in the Brazilian territory in 1994, represents a milestone in the history of health policies in Brazil, as it reorganized the health care model(36). In Minas Gerais, the proportion of the population served in ESF units was 72.3% in 2013, and in 2019, it was 73.0% (37). However, Minas Gerais has its own complexities. In this sense, through the Primary Health Care Secretariat of the Ministry of Health, in May 2019, and with updates to the publication of Ordinance No. 397/GM/MS, of March 16, 2020, the Ministry of Health launched the Saúde na Hora Program, which provides for the extension of opening hours at UBS in municipalities that join the program, enabling easier access for the population to services offered in primary care, including immunization actions(25,38).
Finally, this work demonstrated that, in relation to the proportion of families served by the ESF, the higher their proportions in the municipality were, the greater the VC values for the first and second doses of the HPV vaccine. The second dose applied to females, the area of the municipality, the number of families with a minimum wage and the urbanization rate indicated that the higher the VC values were in the second dose, the lower they were. However, the larger the population of the opposite sex, the greater the percentage of the “poor” population in the single registry and the greater the proportion of families served by the family strategy, the greater the VC in the second dose.
A study by Staples et al. (39) revealed contrasting effects of area-level socioeconomic factors on the initiation and completion of the HPV vaccine among adolescents, with regions with the lowest coverage rates being less populated, less educated, and having a lower median family income and higher rates of poverty and unemployment(39). Among male adolescents, those in these areas had a significantly lower density of primary care providers(39).
Other studies have shown that area-level characteristics such as ethnic composition, population density, sex distribution, area-level socioeconomic status, geographic location, and local health services are associated with geospatial patterns of HPV vaccination coverage in different populations(39,40). As in this study, the work of Grampos et al. showed that the least disadvantaged regions recorded the highest vaccination completion rates, which is consistent with an analysis of secondary data from the 2012 and 2013 NIS-Teen survey. These findings demonstrate that boys who lived in high-poverty areas were more likely to complete the vaccination schedule than boys in low-poverty areas were (41), which is justified by the fact that this more vulnerable population is covered by the health system more effectively.
Nevertheless, in relation to geographic location, studies show that less economically disadvantaged places have more actions related to neighborhood safety; consequently, programs aimed at public health, such as the ESF, are more active and subsidize actions aimed at vaccination programs, which favor higher HPV vaccine rates(42,43).
The limitations of this study are related to the inaccuracy of the use of secondary data regarding VC calculations and data on individual characteristics. On the other hand, the study advances by comparing the cumulative vaccination coverage of the HPV vaccine in multiple cohorts of adolescents to socioeconomic factors and the social environment in the state of Minas Gerais. It is also worth highlighting the innovation of this study regarding adolescent health and vaccination, a topic that is still scarce in the Brazilian and global literature.