Abstract

Objective:

To analyze the temporal trend of human papillomavirus (HPV) vaccination coverage among the female population aged 10 to 14 years, living in the state of Goiás, Brazil, between 2014 and 2022.

Methods:

This was an ecological time series study using data from the Brazilian National Health System Information Technology Department (Departamento de Informática do Sistema Único de Saúde - DATASUS); the annual vaccination coverage rate was calculated based on the number of second doses administered; the trend of the rates was analyzed using the Prais-Winsten model.

Results:

A total of 407,217 second doses of the quadrivalent HPV vaccine were administered to the female population aged 10-14 years, with annual vaccination coverage rates ranging from 12.3% (2019) to 30.0% (2015), and an annual percentage change (APC) of 0.7% (95%CI 0.9; 0.2; p-value = 0.030).

Conclusion:

In Góias state, the quadrivalent HPV vaccine coverage rate was below the national target (80%), showing a stationary trend in the time series.

Keywords:
Human Papillomavirus; Cervical Cancer; Human Papillomavirus Vaccines; Vaccination Coverage; Time Series Studies

Resumen

Objetivo:

Analizar la tendencia temporal de la cobertura de la vacuna contra el virus del papiloma humano (VPH), en la población femenina en Goiás, Brasil, entre 2014 y 2022.

Métodos:

Estudio de serie temporal con datos del Departamento de Informática del Sistema Único de Salud (Datasus); la tasa de cobertura vacunal anual fue calculada por el número de segundas dosis administradas y para el análisis de tendencias se utilizó Prais-Winsten.

Resultados:

Se administraron 407.217 segundas dosis de la vacuna tetravalente contra el VPH en la población femenina de 10 a 14 años en Goiás, con tasas de cobertura vacinal anual variando entre 12,3% (2019) y 30,0% (2015), y una variación porcentual anual (VPA) de 0,7% (IC_95% 0,9;0,2; p-valor = 0,030).

Conclusión:

La tasa de cobertura de la vacuna tetravalente contra el VPH en Goiás quedó por debajo de la meta nacional (80%), con tendencia estacionaria en la serie temporal.

Palabras clave:
Virus del Papiloma Humano; Neoplasias del Cuello Uterino; Vacuna contra el Virus del Papiloma Humano; Cobertura Vacunal; Estudios de Series de Tiempo

Study contributions

Main results

The annual coverage rate of the human papillomavirus (HPV), vaccine among the female population, aged 10-14, in Goiás state was low during the period 2014-2022. Ranging from 12.3% (2019) to 30.0% (2015), with a stationary trend.

Implications for services

Low vaccination coverage results in a greater portion of the population prone to developing cervical cancer and other HPV-related cancers, leading to increased healthcare costs and overwhelmed health system.

Perspectives

Further studies of the factors associated with refusal or voluntary delay in HPV vaccination in Goiás state are suggested, as well as analysis of coverage rates during vaccination campaigns to assess their impact on vaccination rates.

Keywords:
Human Papillomavirus; Cervical Cancer; Human Papillomavirus Vaccines; Vaccination Coverage; Time Series Studies

INTRODUCTION

It is estimated that approximately 13% of all cancer cases worldwide - excluding non-melanoma skin cancer - are related to infections.¹1. International Agency for Research on Cancer. Cancer today. Data visualization tools for exploring the global cancer burden in 2020 [Internet]. Lyon: International Agency for Research on Cancer; 2020 [cited 2022 Aug 12]. Available from: https://gco.iarc.fr/today/home.
https://gco.iarc.fr/today/home... Among the infectious agents causing the disease, the human papillomavirus (HPV) stands out, with infections linked to several types of cancers, such as cervical cancer, anus, penis, vulva and oropharyngeal.²2. International Agency for Research on Cancer. Human Papillomavirus and related diseases report. [Internet]. Lyon: International Agency for Research on Cancer; 2021 [cited 2022 Nov 12]. Available from: https://www.iarc.who.int/.
https://www.iarc.who.int/...

Cervical cancer is the fourth most common cancer in women globally and the third in Brazil, with a high associated mortality rate.³3. World Health Organization. Cervical Cancer. Geneva: World Health Organization, 2021. cited 2022 Aug 13]. Available from: Available from: https://www.paho.org/en/topics/cervical-cancer .
https://www.paho.org/en/topics/cervical-... In 2020, over 600,000 cases of cervical cancer were estimated worldwide, with an incidence of 13.3 cases per 100,000 women and a mortality rate of 7.2 deaths per 100,000 women per year. The highest incidence is concentrated in populous countries such as Indonesia, India, Russia and Brazil.⁴4. Singh D, Vingnat J, Lorenzoni V, Eslahi M, Ginsburg O, Lauby-Secretan B, et al. Global estimates of incidence and mortality of cervical cancer in 2020: a baseline analysis of the WHO Global Cervical Cancer Elimination Initiative. Lancet Glob Health. 2023;11(2):e197-e206. DOI:10.1016/S2214-109X(22)00501-0.
https://doi.org/10.1016/S2214-109X(22)00...

HPV vaccination is the primary means of preventing cervical cancer, with efficacy already demonstrated in several studies.⁵5. Lei J, Ploner A, Elfström KM, Wang J, Roth A, Fang F, et al. HPV Vaccination and the risk of invasive cervical cancer. N Engl J Med 2020;383:(14)1340-8. DOI: 10.1056/NEJMoa1917338
https://doi.org/10.1056/NEJMoa1917338... ^),(66. Drolet M, Bénard E, Pérez N, Brisson M, HPV Vaccination Impact Study Group. Population-level impact and herd effects following the introduction of human Papillomavirus vaccination programmes: updated systematic review and meta-analysis. Lancet. 2019;394(10197):497-509. DOI: 10.1016/S0140-6736(19)30298-3.
https://doi.org/10.1016/S0140-6736(19)30... In Brazil, a large study showed a 56.8% reduction in the prevalence of HPV genotypes identified as HPV 6, 11, 16 and 18 among vaccinated women aged 16 to 25 years.⁷7. Wendland EM, Kops NL, Bessel M, Comerlato J, Maranhão AGK, Souza FMA, et al. Effectiveness of a universal vaccination program with an HPV quadrivalent vaccine in young Brazilian women. Vaccine. 2021;39:1840-1845. doi: 10.1016/j.vaccine.2021.02.040.
https://doi.org/10.1016/j.vaccine.2021.0...

Quadrivalent HPV vaccine, aimed at adolescents aged 9 to 14 years and immunocompromised people, regardless of age, has been offered by the National Immunization Program (Programa Nacional de Imunizações - PNI) since 2014, in Brazil. The quadrivalent vaccine provides protection against HPV types 16 and 18, which have high oncogenic potential; in addition to types 6 and 11, which pose low oncogenic risk, despite being the main cause of anogenital warts.⁸8. Ministério da Saúde (BR). Secretaria de Vigilância em Saúde. Departamento de Vigilância das Doenças Transmissíveis. Coordenação-Geral do Programa Nacional de Imunizações. Informe técnico da ampliação da oferta das vacinas papilomavírus humano 6, 11, 16 e 18 (recombinante) - vacina HPV quadrivalente e meningocócica C (conjugada) [Internet]. Brasília: Ministério da Saúde; 2018 [citado 2023 Jan 15]. Disponível em: Disponível em: https://portalarquivos2.saude.gov.br/images/pdf/2018/marco/14/Informe-T--cnico-HPV-MENINGITE.pdf .
https://portalarquivos2.saude.gov.br/ima...

Following the inclusion of the HPV vaccine in the Brazilian immunization schedule, additional strategies were implemented over time, aimed to achieve the national coverage target of 80%. Among these strategies are (i) the provision of the vaccine in school settings, (ii) the inclusion of male children and adolescents as the target population, with a gradual reduction of the minimum age to 9 years, and (iii) the inclusion of specific population groups, such as the immunocompromised individuals, who receive the vaccine in a three-dose schedule.⁸8. Ministério da Saúde (BR). Secretaria de Vigilância em Saúde. Departamento de Vigilância das Doenças Transmissíveis. Coordenação-Geral do Programa Nacional de Imunizações. Informe técnico da ampliação da oferta das vacinas papilomavírus humano 6, 11, 16 e 18 (recombinante) - vacina HPV quadrivalente e meningocócica C (conjugada) [Internet]. Brasília: Ministério da Saúde; 2018 [citado 2023 Jan 15]. Disponível em: Disponível em: https://portalarquivos2.saude.gov.br/images/pdf/2018/marco/14/Informe-T--cnico-HPV-MENINGITE.pdf .
https://portalarquivos2.saude.gov.br/ima...

However, little information is available about the impact of these actions on the temporal evolution of vaccination coverage in each Federative Unit, which makes it difficult to formulate specific strategies for each population and geographic region.⁸8. Ministério da Saúde (BR). Secretaria de Vigilância em Saúde. Departamento de Vigilância das Doenças Transmissíveis. Coordenação-Geral do Programa Nacional de Imunizações. Informe técnico da ampliação da oferta das vacinas papilomavírus humano 6, 11, 16 e 18 (recombinante) - vacina HPV quadrivalente e meningocócica C (conjugada) [Internet]. Brasília: Ministério da Saúde; 2018 [citado 2023 Jan 15]. Disponível em: Disponível em: https://portalarquivos2.saude.gov.br/images/pdf/2018/marco/14/Informe-T--cnico-HPV-MENINGITE.pdf .
https://portalarquivos2.saude.gov.br/ima... Furthermore, studies show highly heterogeneous vaccination coverage in the country, with high dropout rates after the first dose and greater difficulty accessing some locations, including the state of Goiás.⁶6. Drolet M, Bénard E, Pérez N, Brisson M, HPV Vaccination Impact Study Group. Population-level impact and herd effects following the introduction of human Papillomavirus vaccination programmes: updated systematic review and meta-analysis. Lancet. 2019;394(10197):497-509. DOI: 10.1016/S0140-6736(19)30298-3.
https://doi.org/10.1016/S0140-6736(19)30... ^),(77. Wendland EM, Kops NL, Bessel M, Comerlato J, Maranhão AGK, Souza FMA, et al. Effectiveness of a universal vaccination program with an HPV quadrivalent vaccine in young Brazilian women. Vaccine. 2021;39:1840-1845. doi: 10.1016/j.vaccine.2021.02.040.
https://doi.org/10.1016/j.vaccine.2021.0... ^),(99. Moura LL, Codeço CT, Luz PM. Cobertura da vacina papilomavírus humano (HPV) no Brasil: heterogeneidade espacial e entre coortes etárias. Rev. bras. epidemiol. 2021 [; 24: E210001. doi: 10.1590/1980-549720210001.
https://doi.org/10.1590/1980-54972021000...

The objective of this study was to analyze the temporal trend of HPV vaccination coverage among the female population aged 10 to 14 years, living in the state of Goiás, Brazil, between 2014 and 2022.

METHODS

This was an ecological time series study conducted in Goiás state, Brazil. The state of Goiás, located in the Midwest region of the country, covers an area of 340,242.859 km² and had an estimated population of 7,056,495 inhabitants (2022), 50.9% of whom were female.¹⁰10. Instituto Brasileiro de Geografia e Estatística (BR). Censo Demográfico 2022: Populações e domicílios - Primeiros resultados [Internet]. Rio de Janeiro: Instituto Brasileiro de Geografia e Estatística; 2023. [citado 2024 Fev 10]. Disponível em: Disponível em: https://biblioteca.ibge.gov.br/index.php/biblioteca-catalogo?view=detalhes&id=2102011 ..
https://biblioteca.ibge.gov.br/index.php...

The study participants were comprised of females, aged 10 to 14 years, living in Goiás state from 2014 to 2022. The study variables were: the number of second doses of the HPV vaccine administered each year between 2014 and 2022; and the number of females aged 10 to 14 years, living in Goiás in each year of the study.

The number of second doses administered/year in the study population was retrieved from the National Immunization Program Information System (Sistema de Informações do Programa Nacional de Imunizações - SI-PNI), linked to the Brazilian National Health System Information Technology Department (Departamento de Informática do Sistema Único de Saúde - DATASUS), using an online data tabulator and spreadsheet generator tool: TabNet - Health Care module. The target population was obtained from the population estimates of the Brazilian Institute of Geography and Statistics (Instituto Brasileiro de Geografia e Estatística - IBGE), filtering the data by location and year.¹¹11. Instituto Brasileiro de Geografia e Estatística (BR). Projeções da População do Brasil e Unidades da Federação por sexo e idade: 2010-2060 [Internet]. Rio de Janeiro: Instituto Brasileiro de Geografia e Estatística; 2018 [citado 2023 Abr 12]. Disponível em: Disponível em: https://www.ibge.gov.br/estatisticas/sociais/populacao/9109-projecao-da-populacao.html .
https://www.ibge.gov.br/estatisticas/soc... The databases were accessed on February 20, 2023.

As for the calculation of the vaccination coverage rate, the methodology proposed by the Pan American Health Organization/World Health Organization (PAHO/WHO) was used: as numerator, the number of second doses administered in the target population, and as denominator, the size of the target population, multiplied by 100.¹²12. Organização Pan-Americana da Saúde. Metodologia para o cálculo de cobertura da vacina contra o HPV na Região das Américas [Internet]. Washington: Organização Panamericana da Saúde; 2019 [citado 2020 Ago 10]. 18 p. Disponível em: Disponível em: https://iris.paho.org/handle/10665.2/51663 .
https://iris.paho.org/handle/10665.2/516...

Regarding trend analysis, the Prais-Winsten model, proposed by Antunes & Cardoso, was used, considering time as the independent variable; and the annual vaccination coverage rate transformed into a base-10 logarithmic function as the dependent variable.¹³13. Antunes JLF, Cardoso MRA. Uso da análise de séries temporais em estudos epidemiológicos. Epidemiol Serv Saude. 2015;24(3):565-76. doi: 10.5123/S1679-49742015000300024.
https://doi.org/10.5123/S1679-4974201500... The annual percentage change (APC) was obtained using the formula:

[(vaccination coverage rate in the following year ÷ vaccination coverage rate in the previous year) - 1] × 100

The value of which can indicate an increasing, decreasing, or stationary trend in the time series.¹³13. Antunes JLF, Cardoso MRA. Uso da análise de séries temporais em estudos epidemiológicos. Epidemiol Serv Saude. 2015;24(3):565-76. doi: 10.5123/S1679-49742015000300024.
https://doi.org/10.5123/S1679-4974201500...

The Durbin-Watson test was applied to check for the presence of serial autocorrelation, with values close to two indicating the absence of serial autocorrelation. The data were tabulated and analyzed using Excel and Stata 17.0 software, respectively.

Taking into consideration its observational nature and the use of data in the public domain, this study did not require ethical review.¹⁴14. Brasil. Ministério da Saúde. Conselho Nacional de Saúde. Resolução no 510, de 7 de abril de 2016. Trata sobre as diretrizes e normas regulamentadoras de pesquisa em ciências humanas e sociais [Internet]. Diário Oficial da União, Brasília (DF), 2016 Maio 24 [citado 2023 Ago 11], Seção 1:44. Disponível em: Disponível em: https://bvsms.saude.gov.br/bvs/saudelegis/cns/2016/res0510_07_04_2016.html .
https://bvsms.saude.gov.br/bvs/saudelegi... The drafting of the article followed the recommendations of the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) and The Reporting of Studies Conducted Using Observational Routinely Collected Health Data (RECORD).¹⁵15. von Elm E, Altman DG, Egger M, Pocock SJ, Gøtzsche PC, Vandenbroucke JP; et al. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies. J Clin Epidemiol. 2008;61(4):344-9. doi: 10.1016/j.jclinepi.2007.11.008.
https://doi.org/10.1016/j.jclinepi.2007.... ^),(1616. Benchimol EI, Smeeth L, Guttmann A, Harron K, Moher D, Petersen I, et al. The REporting of studies Conducted using Observational Routinely-collected health Data (RECORD) statement. PLoS Med. 2015;12(10):e1001885. doi: 10.1371/journal.pmed.1001885.
https://doi.org/10.1371/journal.pmed.100...

RESULTS

Between 2014 and 2022, a total 407,217 second doses of the quadrivalent HPV vaccine were administered to the female population aged between 10 and 14 years in the state of Goiás. The highest vaccination coverage rates were observed in 2015 and 2014, as shown in Table 1.

The annual vaccination coverage rate ranged from 12.3% in 2019 to 30.0% in 2015. The APC was 0.7% (95%CI 0.9; 0.2; p-value = 0.030), and the temporal trend was considered stationary (Figure 1).

The Durbin-Watson test showed a coefficient of 2.98, excluding the hypothesis of serial autocorrelation: there was no correlation between the current vaccination coverage rate and the vaccination coverage rate in previous years. Thus, it is assumed that the findings occurred randomly and independently.

DISCUSSION

This study showed low HPV vaccine coverage among female adolescents in the state of Goiás, with a stationary trend in the time series. This scenario is concerning and demands careful attention from local management, based on the target set by the WHO for the elimination of cervical cancer worldwide, aiming to achieve a vaccination coverage of 90% by 2030.¹⁷17. World Health Organization. Global strategy to accelerate the elimination of cervical cancer as a public health problem. Geneva: World Health Organization , 2020 [cited 2023 Aug 14]. Disponível em: Disponível em: https://www.who.int/publications/i/item/9789240014107 .
https://www.who.int/publications/i/item/...

Low HPV vaccination coverage is a global reality, especially in developing countries. There is a significant disparity in vaccination rates between developed and least developed countries, as well as variations in the quality of vaccination records.¹⁸18. Spayne J, Hesketh T. Estimate of global human papillomavirus vaccination coverage: analysis of country-level indicators. BMJ Open. 2021;11(9):e052016. doi: 10.1136/bmjopen-2021-052016.
https://doi.org/10.1136/bmjopen-2021-052... The estimated global HPV vaccination coverage in 2018 was only 12.2%.¹⁷17. World Health Organization. Global strategy to accelerate the elimination of cervical cancer as a public health problem. Geneva: World Health Organization , 2020 [cited 2023 Aug 14]. Disponível em: Disponível em: https://www.who.int/publications/i/item/9789240014107 .
https://www.who.int/publications/i/item/... According to WHO estimates, the Region of the Americas showed the highest percentage of girls vaccinated by age 15, with vaccination coverage reaching 64% in 2021 and 66% in 2022; for the same periods, respectively, this coverage was 28% and 29%, in Europe, 18% and 19%, in Africa, and below 2% in Asia and the Middle East, reflecting a possible cultural determinant impacting the differences observed in the demand for and availability of the HPV vaccine, according to regions and continents.¹⁹19. World Health Organization. Human Papillomavirus (HPV) vaccination coverage. Geneva: World Health Organization; 2021 [cited 2023 Dec 11]. Available from: Available from: https://immunizationdata.who.int/pages/coverage/hpv.html?GROUP=WHO_REGIONS&ANTIGEN=15HPVC_F&YEAR=&CODE= .
https://immunizationdata.who.int/pages/c...

In Canada, HPV vaccination coverage in 2021 ranged from 57.1 to 91.3% depending on the region, while in the United States it remained around 76.9% in the same year.²⁰20. Canadian Partnership Against Cancer. HPV immunization for the prevention of cervical cancer. Toronto: Canadian Partnership Against Cancer; 2021 [cited 2023 Dec 11].. 36 p. Available from: Available from: https://s22457.pcdn.co/wp-content/uploads/2021/04/HPV-immunization-prevention-cervical-cancer-EN.pdf .
https://s22457.pcdn.co/wp-content/upload... ^),(2121. Pingali C, Yankey D, Elam-Evans LD, Markowitz LE, Valier MR, Fredua B, et al. National Vaccination Coverage Among Adolescents Aged 13-17 Years — National Immunization Survey-Teen, United States, 2021. MMWR Morb Mortal Wkly Rep. 2022;71(35):1101-8. doi: 10.15585/mmwr.mm7135a1
https://doi.org/10.15585/mmwr.mm7135a1... In Latin American countries, however, vaccination coverage in 2020 ranged from 7% to 77% among female populations in the Dominican Republic and Costa Rica, respectively; in some countries in the region, such as Cuba, Venezuela, and Nicaragua, at the time this report was completed, there was no HPV vaccination plan among public immunization policies.²²22. Nogueira-Rodrigues A, Flores MG, Macedo Neto AO, Braga LAC, Vieira CM, Sousa-Lima RM, et al. HPV vaccination in Latin America: Coverage status, implementation challenges and strategies to overcome it. Front Oncol. 2022;12:984449. doi: 10.3389/fonc.2022.984449.
https://doi.org/10.3389/fonc.2022.984449... In Brazil, vaccination coverage rates vary according to region, socioeconomic factors, and age group, although they remain below the national target of 80% in all regions of the country.⁹9. Moura LL, Codeço CT, Luz PM. Cobertura da vacina papilomavírus humano (HPV) no Brasil: heterogeneidade espacial e entre coortes etárias. Rev. bras. epidemiol. 2021 [; 24: E210001. doi: 10.1590/1980-549720210001.
https://doi.org/10.1590/1980-54972021000...

In addition to the low adherence to HPV vaccination in Goiás, the results of this study show a decrease of over 50% in the rates of administration of the second dose of the HPV vaccine between 2015 and 2016, a period corresponding to the second year, post-introduction of the quadrivalent HPV vaccine into the Brazilian immunization schedule. From that point onwards, vaccination coverage maintains a stationary trend until the end of the time series evaluated. Corroborating these results, another Brazilian study showed a reduction of almost 30% in the number of doses of the HPV vaccine administered between 2014 and 2018, with an even sharper decline from 2015 onwards. In the Midwest region, for example, 596,777 doses were administered in 2014 and 176,935 in 2018, specifically in Goiás, this number dropped from 244,285 to 70,915 doses during the same period.²³23. Castro BT, Quaresma ALP, Azevêdo AO, Silva LM, Teixeira CSS. Coverage of doses of the HPV vaccine and variation by level of material deprivation in brazilian municipalities, 2012 to 2018. Res Soc Dev. 2022;11(13):e271111335484. doi: 10.33448/rsd-v11i13.35484.
https://doi.org/10.33448/rsd-v11i13.3548... This sharp decline after 2015 is possibly related to the cessation of the initial efforts for dissemination and expansion of supply, which were undertaken during the stage of the implementation of the vaccine into the recommended immunization schedule.²³23. Castro BT, Quaresma ALP, Azevêdo AO, Silva LM, Teixeira CSS. Coverage of doses of the HPV vaccine and variation by level of material deprivation in brazilian municipalities, 2012 to 2018. Res Soc Dev. 2022;11(13):e271111335484. doi: 10.33448/rsd-v11i13.35484.
https://doi.org/10.33448/rsd-v11i13.3548...

Low adherence to the HPV vaccine is multifactorial. Studies demonstrate that income, race/skin color, education level, and geographic conditions can constitute barriers to the population access to the vaccine.⁹9. Moura LL, Codeço CT, Luz PM. Cobertura da vacina papilomavírus humano (HPV) no Brasil: heterogeneidade espacial e entre coortes etárias. Rev. bras. epidemiol. 2021 [; 24: E210001. doi: 10.1590/1980-549720210001.
https://doi.org/10.1590/1980-54972021000... ^),(2424. Carvalho AMC, Andrade EMLR, Nogueira LT, Araújo TME. HPV vaccine adherence among adolescentes: integrative review. Texto & Contexto Enferm. 2021;28:e20180257. doi: 10.1590/1980-265X-TCE-2018-0257.
https://doi.org/10.1590/1980-265X-TCE-20... ^),(2525. Oliveira PS, Gonçalves CV, Watte G, Costa JSD. Cobertura vicinal contra o papiloma virus humano (HPV) e fatores associados em acadêmicas de uma universidade do sudoeste goiano. Rev Saude Publica. 2021;55:65. doi: 10.11606/s1518-8787.2021055003144.
https://doi.org/10.11606/s1518-8787.2021... Lack of knowledge, fear of adverse events, traditional beliefs and values, and the association of the vaccine with early sexual initiation can also lead to its refusal, both by adolescents and by their parents, resulting in low HPV vaccination coverage rates.²⁶26. Zheng L, Wu J, Zheng M. Barriers to and facilitators of human papillomavirus vaccination among people aged 9 to 26 years: a systematic review. Sex Transm Dis. 2021;48(12):p e255-e262. doi: 10.1097/OLQ.0000000000001407.
https://doi.org/10.1097/OLQ.000000000000... ^),(2727. Aps LRMM, Piantola MAF, Pereira SA, Castro JT, Santos FAO, Ferreira LCS. Adverse events of vaccines and the consequences of non-vaccination: a critical review. Rev Saude Publica. 2018;52:40. doi: 10.11606/S1518-8787.2018052000384
https://doi.org/10.11606/S1518-8787.2018... In this context, there is a need to expand access to the vaccine, especially in less-developed regions, in addition to the implementation of educational actions, communication campaigns, and specific policies aimed at increasing engagement and acceptance of vaccination. Dialogues with community and/or religious leaders can be effective strategies for achieving the immunization targets.

Another interesting aspect addressed in the literature is the difference in coverage between the first and second doses, indicating that a portion of the population initiates the HPV vaccination schedule but does not complete it. This phenomenon, known as vaccine dropout, has been reported more frequently in the child population, with regard to the essential vaccines in the schedule, and may be associated with a drop in immunobiological coverage of up to 40%.²⁸28. Oliveira WL, Dantas S, Guimarães AS, Salvador Júnior G, Silva JV, Ferreira VS, et al. Indicators of vaccination coverage/ dropout rate in the capitals of the northern region of Brazil: a challenge to popular education in health from the perspective of Primary Health Care. Braz J Develop. 2022;8(5):33779-89. doi: 10.34117/bjdv8n5-076.
https://doi.org/10.34117/bjdv8n5-076... ^),(2929. Moura LL, Neto M, Souza-Santos R. Temporal trend of the dropout rate and vaccination coverage of the triple viral vaccine in Brazil, 2014-2021. Epidemiol Serv Saude. 2023;32(3):e2023117. doi: 10.1590/S2237-96222023000300004.pt.
https://doi.org/10.1590/S2237-9622202300... Although evidence of this phenomenon in HPV vaccination is scarce, it is likely that the low vaccination coverage found is related to high rates of vaccination dropout, given that this analysis only took into consideration adolescents who had received the second dose of the vaccine. Currently, the effectiveness of the one-dose HPV vaccine for the prevention of cervical cancer is being studied, a measure that could result in increased supply and greater population adherence.³⁰30. Villa LL, Richtmann R. HPV vaccination programs in LMIC: is it time to optimize schedules and recommendations? J Pediat. 2023;99(Suppl 1):S57-S61. doi: 10.1016/j.jped.2022.11.012.
https://doi.org/10.1016/j.jped.2022.11.0...

The data presented in this study are of great regional interest, given the scarcity of research on HPV vaccine coverage among the female population living in the state of Goiás. The stationary trend in coverage rates, observed for most of the time series, suggests a possible inefficiency in vaccination strategies, associated with low interest and knowledge of the population about the importance of the vaccine. It was expected that the COVID-19 pandemic would influence the vaccination trend in recent years, which was not confirmed.

This study has limitations related to the use of secondary data, due to the possibility of poor quality of records and consequent discrepancy in available information. In addition, no stratified analysis was conducted by age and municipalities, nor were possible vaccination patterns in males investigated. For further studies, it is suggested to investigate the local factors leading to the refusal or voluntary delay in HPV vaccination, as well as seasonal analyses during vaccination campaigns and their impact on the vaccination rates achieved.

It can be concluded that the coverage rate of the quadrivalent vaccine against the HPV in Goiás state was below the national target between 2014 and 2022, showing a stationary trend in this time series. As additional measures to address the issue, it is suggested that (i) the opportunity for “extramural” vaccination activities - in schools, churches and other places with a large concentration of adolescents - be provided, as well as (ii) the active search for those who are missing vaccinations, based on data concerning vaccination dropout after the first dose.

REFERENCES

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