The World Health Organization (WHO) defines a Sexually Transmitted Infection (STI) as an infection that is transmitted during unprotected sexual intercourse [1].

In the world, the most common STIs are: gonococcal, chlamydia, hepatitis B, genital herpes, HPV infection, mycoplasma infections, trichomonas, and HIV infection [2].

In most cases, sexually transmitted infections are asymptomatic, and the clinical picture is often that of complications that involve the functional (tubal sterility) and vital (AIDS) prognosis.

In France, the most well-known STI among adolescents is HIV infection because, in this study, 85% of adolescents had good knowledge about it [3].

Indeed, the highest STI rates are usually found in young people aged 15 to 24. It is in this context that we carried out this work to evaluate the knowledge and behavior of adolescents regarding sexuality, sexually transmitted infections, and human papillomavirus vaccination in Libreville.

It was a cross-sectional, descriptive, and analytical study that took place from December 2022 to June 2023 in public and private high schools in the municipalities of Libreville, Owendo, and Akanda.

We targeted in-school adolescents who ranged between 13- and 19-years old living in the Gabonese capital because they are the most exposed section of the population to STIs, and they are the target of HPV vaccination.

Inclusion criteria:

All teenagers aged 13 to 19 who were present in classrooms on the day of the survey and agreed to participate. All returned forms were included, even if partially completed.

Exclusion criteria:

Adolescents younger than 13 years or older than 19 years old on the survey day, those absent during data collection, and those who refused to participate.

The survey sheet was an individual and anonymous questionnaire consisting of four sections: the first collected the sociodemographic data of adolescents; the second made it possible to evaluate the knowledge of adolescents on STIs and was made up of 32 questions; the third section described the sexuality and behavior of adolescents; and the last section finally evaluated the knowledge of adolescents in relation to HPV vaccination and consisted of 7 questions.

Data were entered in CSPro 6.3 and analyzed in SPSS Version 20. We computed means and standard deviation for quantitative variables and applied Pearson’s chi-square test, with p < 0.05 considered statistically significant.

Sample size

The minimum sample size was determined for a single proportion with two-sided α = 0.05, precision d = 0.05, using N = Z² × P(1 − P)/ d² with Z = 1.96. In the absence of a robust prior estimate for the target population, we used P = 50% (maximum variance), as recommended by WHO (Lwanga & Lemeshow).

Ethics

The approval was obtained from the National Ethics Committee of Gabon and the hospital. The confidentiality and anonymity of the patient were strictly respected, in accordance with the ethical guidelines, Decree 00732/PR/MRSDT of September 15, 2008, setting out the composition and functioning of the National Ethics Committee.

For this study, 1,500 questionnaires were distributed, and 1,163 were recovered, including those incompletely completed, resulting in a participation rate of 78%. The average age of school adolescents was 16.6 years, with extremes of 13 years and 19 years. Sixteen- and seventeen-year-olds were the largest groups in our sample (n = 232 and n = 234, respectively).

Adolescents from single-parent families comprised 49.6% of the sample; 6.8% did not report their parents’ marital status.

Table 1. Distribution of adolescents by knowledge of STIs.

HIV was the most commonly recognized STI: among adolescents who reported about STIs, 1099 (94.5%) named HIV (Table 1), followed by gonorrhea (67.5%) and syphilis (62.4%). Television was the leading information source, cited by 45.7% of those aware of STIs. AIDS was also the STI that adolescents reported fearing the most. Testicular pain was the most frequently cited symptom of STI, mentioned by 224 adolescents (19.26%). Third-grade students were the largest subgroup, accounting for 38.8% of participants. Among 935 adolescents, 74.4% were unaware of HPV; only 159 knew about the HPV vaccine, and 5.7% had received at least one dose. The mean HPV knowledge score was 3.6/20. The HPV-cervical cancer link was not known to 61.3% of adolescents.

Pharmacies were the commonly cited source of condoms, reported 948 times (81.5%) among adolescents aware of STIs. A majority (711; 61.1%) believed they knew at least one route of STI transmission. Unprotected sexual intercourse was the route most frequently mentioned by 687 adolescents (96.6%) of those claiming such knowledge. Condom use at first intercourse was reported by 64.6% of sexually active adolescents. There was no significant association between parents’ marital and the age at first sexual intercourse (p = 0.077; Table 2).

Table 2. Age at first sexual intercourse by parents’ marital status among adolescents.

Parents’ occupational category (OC) was not significantly associated with adolescents’ age at sexual debut (p = 0.128; Table 3).

Table 3. Age at first sexual intercourse by parents’ occupational category. (OC)

Nearly all adolescents (98.8%) had low knowledge of STIs. STI knowledge did not differ significantly by parents’ occupational category (p = 0.183). The mean STI knowledge score was 5.6/20.

Limitations of the study:

This study was conducted in public and private schools in Libreville; results may not generalize to adolescents who are out of school. Questionnaires were completed in classrooms on the day of data collection, where privacy was difficult to ensure, potentially introducing social desirability and reporting biases. Because sexuality remains a sensitive topic in this setting, many adolescents may rely primarily on mass media for information, which could have influenced their answers. Regarding sexual debut, some adolescents reported first intercourse before age 15, 64% between 15 - 18 years, and nearly 3% after 18 years, suggesting an early onset of sexual activity in this context (and possibly earlier than in other countries).

In France, outcomes appear more favorable: in Grondin et al [4], most adolescents reported using contraception at first intercourse, with male condoms as the preferred method.

Consequently, condom use appears to be declining among Gabonese adolescents, potentially increasing the risks and adverse consequences of unprotected sexual activity.

In Morocco, El Yahyaoui et al. [5] reported a different pattern: while HIV remained the best known STI among adolescents, syphilis ranked second and gonorrhea third. In urban Casablanca, adolescents who had heard of at least one STI most frequently cited AIDS (95.8%), followed by syphilis (56.8%) and gonorrhea (38.6%); In a semi-urban area of Marrakech, the corresponding proportions were 94.2%, 44.3%, and 32.9%, respectively. In Switzerland, Beck et al. [6] found higher awareness levels: 93% had heard of HPV and 88% knew about the vaccine, likely reflecting school-based vaccination campaigns, whereas in our setting, efforts are still focused on raising awareness. In France, Curry et al. [7] reported that 49% of girls had received ≥ 1 HPV dose in 2012; among those vaccinated, nearly two-thirds did so mainly on the advice of a physician or parents, consistent with Blumberg et al. [8]. In our sample, practical attitudes score towards STIs averaged 5.2/20, indicating poor overall adherence to recommend practices and limited engagement with STI awareness campaigns.

Regarding HPV vaccination coverage in France, Lerais et al. [9] estimated 47% for at least one dose in 2013, but other reports indicate substantially lower national coverage (17.2%), with Bruni et al. [10], and Goldie et al. [11] citing even lower figures. Parents’ marital status was not associated with the age at first sexual intercourse among adolescents (p = 0.77).

In this survey in Libreville assessing adolescents’ knowledge, attitudes, and practices regarding sexuality, STIs, and HPV vaccination, adolescents showed low overall knowledge of STIs and HPV, and risky sexual behaviors persisted across sexes. HPV vaccination coverage was very low in our sample. To strengthen adolescent knowledge and prevention, targeted awareness campaigns remain the preferred strategy in this context and should be delivered through digital and social platforms that are widely accessible to this age group.