This study adopted a cross-sectional design to estimate the prevalence of dual protection use among adolescent girls. Subsequently, to identify factors associated with dual protection, a nested age-matched case-control study was conducted within the same population, comparing adolescents who reported using dual protection (cases) with those who did not (controls). This study was conducted over 10 months, from November 1^rst 2023, to August 31, 2024, at the Maroua Regional Hospital, a 3rd category and 2nd referral level facility, serving as a referral center for several health facility and district hospitals in the Far North region of Cameroon.

The study was carried out in the different departments of the Maroua Regional hospital, with a particular focus on the Adolescent Reproductive Health Service (ARH), which receives an average of 90 adolescent girls per month and offers sexual and reproductive health services, including family planning and management of unwanted pregnancies.

The target population included all adolescent girls using modern contraceptive methods. The study population consisted of adolescent girls aged 15 to 19, using modern contraceptive methods and attending consultation at the Maroua Regional Hospital during the study period and meeting the inclusion criteria.

A consecutive non-probability sampling method was applied. All eligible adolescent girls attending consultation during the study period were invited to participate. The minimum sample size was calculated according to the Schlesselman formula, for comparing two proportions, with a two-sided significance level of 5% and a statistical power of 80%. We considered a proportion of adolescents using dual protection (p₁ = 13.3%) [8] . and a proportion of those using modern contraception (p₂ = 48.7%). The minimum required sample size was 26 participants per group (52 in total). Allowing for a 10% non-response rate, the final sample size was set at 58 participants.

After obtaining ethical and administrative approvals, eligible adolescent girls were informed about the study and invited to participate. After obtaining parental consent and participant assent for those less than 18 years old, a structured pre-tested questionnaire was administered individually, in French or the local language.

The data collected included:

Data were entered into Excel and analyzed using Epi Info 7.2. Descriptive statistics were employed to summarize the characteristics of the sample and patterns of dual protection use. Associations between dual protection use and explanatory variables were evaluated using the chi-square test. Variables with a p-value < 0.05 in bivariate analyses were included in a multivariate logistic regression model to identify independent predictors of dual protection use. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated, and a p-value < 0.05 was considered statistically significant.

The study was approved by the Institutional Ethics and Research Committee of the Faculty of Medicine and Biomedical Sciences of the University of Yaoundé I and by the Institutional Ethics Committee for Human Health Research of the Far North Regional Delegation. Written informed consents from participants aged ≥18 were obtained. Informed consent from parents and assent from the adolescent girls < 18 were obtained. Confidentiality and anonymity of the participants were strictly respected.

A total of 103 adolescent girls were recruited for the study. Twelve were excluded due to incomplete medical records, resulting in 91 eligible participants. Following age-based matching, 31 participants were excluded, and 60 were retained for analysis ( Figure 1 ). These were matched in a 1:1 ratio, comprising 30 adolescents in the single-contraception group and 30 in the dual-contraception group. The final study sample therefore consisted of 60 participants.

The mean age of the adolescent girls was 18.0 ± 1.2 years (15 - 19 years). The majority of participants were from the Far North region (76.7%), Muslim (41.7%), with a secondary education (56.7%), and residing in urban areas (70%) ( Table 1 ).

Of the 91 teenage girls selected with complete records, 30 (32.9%) used dual protection. These were mainly those aged 19 years and who had a secondary level of education. Univariate analysis showed that married adolescents were significantly less likely to use dual protection compared to those with a non-cohabiting partner (OR = 0.31; 95% CI: 0.08 - 0.72; p = 0.008) ( Table 2 ).

Dual protection was used more by adolescents who had their first sexual intercourse after 15 years (85%). History of STIs (40% vs 23.3%; OR = 2.19; 95% CI: 1.04 - 6.69; p = 0.041) and previous pregnancy (66.7% vs 46.7%; OR = 2.29; 95% CI: 1.09 - 6.49; p = 0.038) were significantly associated with the use of dual protection. Bivariate analysis revealed that adolescents with a history of sexually transmitted infections were more likely to adopt dual protection (40% vs 23.3%; OR = 2.19; 95% CI: 1.04 - 6.69; p = 0.041). Similarly, those with a previous pregnancy had increased odds of dual protection (66.7% vs 46.7%; OR = 2.29; 95% CI: 1.09 - 6.49; p = 0.038). Use of oral pills (OR = 4.12, 95% CI 1.39 - 12.26, p = 0.011) and male condoms (OR = 6.99, 95% CI 1.38 - 35.46, p = 0.018) were also positively associated with dual protection. Conversely, adolescents using long-acting reversible contraceptives (LARC) such as IUDs (OR = 1.02 [0.36 - 2.92], p = 0.97), implants (OR = 1.73 [0.59 - 5.06], p = 0.32), or injectable (OR = 2.14 [0.46 - 9.97], p = 0.55) were less likely to use dual protection ( Table 3 ).

STI = Sexually transmitted infection.

All adolescents had heard of contraception, but only 53.3% had attended family planning service. Knowledge of pills (OR = 4.12; 95% CI: 1.39 - 12.26; p = 0.011) and male condoms (OR = 6.99; 95% CI: 1.38 - 35.46; p = 0.018) was positively associated with the use of dual protection ( Table 4 ).

In addition, all adolescents using dual protection had heard of it, mainly during educational talks (33.3%) and through the media (16.7%). Belief that dual protection is effective was strongly associated with its use (OR = 14.0; 95% CI: 3.66 - 53.59; p = 0.002) ( Table 5 ).

The male condom was the most commonly used method, alone or in combination. All adolescent girls using dual protection reported using it consistently, and it was the factor most strongly associated with the adoption of this strategy (OR = 6.99; 95% CI: 1.38 - 35.46; p < 0.001) ( Table 6 ). The most common combination was the association of an injectable contraceptive with the condom (36.6%) ( Figure 2 ).

After adjustment, four independent determinants of the use of dual protection were identified ( Table 7 ). Among adolescents, being married was strongly associated with lower use of dual protection (aOR = 0.14; 95% CI: 0.02 - 0.92; p = 0.041), whereas a history of previous pregnancy (aOR = 2.03; 95% CI: 1.01 - 31.16; p = 0.044), male condom use (aOR = 5.01; 95% CI: 2.51 - 11.67; p = 0.003), and a positive perception of dual protection effectiveness (aOR = 11.1; 95% CI: 1.71 - 71.56; p = 0.011).were all significantly associated with higher uptake. These findings highlight the need for targeted interventions to promote dual protection, particularly among married adolescents, to reduce unintended pregnancies and sexually transmitted infections.

In our study, the average age of adolescent girls was 18.03 years (15 - 19 years). This result is close to that reported by Mekoné et al. (2024) in Yaoundé among sexually active adolescent girls, as well as the 2011 EDS, which placed the median age of first sexual intercourse at 17 years [11] [12] . The literature indicates an average age of 17.6 years for sexual initiation, generally linked to desire, peer influence and curiosity, factors reported by more than half of adolescent girls [13] .

Furthermore, we observed that married adolescent girls were less likely to use dual protection compared with their unmarried peers. This pattern is consistent with findings from other sub-Saharan African studies, where marital status has been identified as a key determinant of contraceptive choice [5] - [7] . This trend could be explained by the fact that: First, married adolescents often perceive themselves at lower risk of sexually transmitted infections (STIs) within the context of a monogamous union, leading to lower condom use despite ongoing risk of HIV or other infections. Second, sociocultural norms and gender dynamics may limit their autonomy in negotiating condom use with spouses [6] [12] . In many settings, married adolescent girls have limited decision-making power regarding reproductive health, and condom use may be stigmatized or perceived as mistrust within marriage [6] [12] . Third, there may be a greater focus on pregnancy prevention via other contraceptive methods, such as pills or injectables, rather than dual protection.

In our study, the majority of adolescents using dual protection had a past history of sexually transmitted infection (46.67%) and unwanted pregnancy (60%). This result is consistent with the results of Kottle et al. (2015) [14] . This could be explained by the fact that prior exposure to STIs may increase awareness of sexual health risks and motivate protective behaviors. These findings align with previous studies showing that personal experience with STIs can enhance risk perception and lead to higher condom use or adoption of dual protection methods [15] . These results suggest that personal experience of a reproductive or infectious risk promotes the adoption of more preventive measures.

Although all participants were aware of contraception in general, only 16 (44.4%) understood the concept of dual protection and its significance.

This study identified the male condom as a strong determinant of dual protection, both in terms of knowledge and actual use. This finding aligns with UNFPA data, which highlight that the condom remains the most well-known and accessible method among adolescent girls in sub-Saharan Africa [16] . Several factors may explain the prominence of condoms. They are widely promoted through public health campaigns, easily available in pharmacies and health centers, and often included in sexual education programs.

However, despite high knowledge and reported use of condoms, dual protection uptake remains low, suggesting that awareness alone is insufficient to ensure consistent practice. Factors such as partner negotiation, sociocultural norms, perceived trust within relationships, and stigma surrounding condom use may limit their wide adoption

After adjustment, four main determinants of dual protection emerged: marital status, pregnancy history, male condom use, and belief in its effectiveness. Married adolescents were less likely to use dual protection, likely due to perceived low STI risk and reliance on hormonal contraception. Prior pregnancy or STI experience increased uptake, suggesting that personal risk motivates protective behavior. Male condom use was the strongest determinant, reflecting its accessibility and dual role in preventing both STIs and pregnancy. Finally, belief in the effectiveness of dual protection influenced adoption, highlighting the importance of knowledge and risk perception. These results are consistent with those of a multinational analysis in West and East Africa, which identified education, reproductive experience, and method perceptions as major determinants of dual contraception use [17] [18] .

These results show that in Cameroon, despite good general awareness of contraception, the understanding and adoption of dual protection remains limited by social and cultural factors. It appears necessary to:

The study has some limitations, including the small sample size and its single-center nature, which limit the generalizability of the results. Data were self-reported, which may be affected by social desirability bias, particularly regarding sexual behavior and contraceptive use. In addition, the relatively small sample size, contributed to wide confidence intervals for several adjusted odds ratios. This reflects limited precision; these findings should therefore be interpreted with caution. Larger, multicenter studies are needed to confirm these associations and provide more precise estimates of the independent predictors of dual protection use.