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HIV/AIDS, Other STIs, and Teen Pregnancy: Group-Based Comprehensive Risk Reduction Interventions for Adolescents


What the Task Force Found

About The Systematic Review

The Task Force finding is based on evidence from a systematic review of 62 studies with 83 study arms (search period 1988 - August 2007). The systematic review was conducted on behalf of the Task Force by a team of specialists in systematic review methods, and in research, practice, and policy related to preventing HIV/AIDS, other STIs, and teen pregnancy.


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Summary of Results

Sixty-two studies with 83 study arms qualified for this review.

  • Results from meta-analyses show that effects were favorable and statistically significant for the following outcomes.
    • Sexual activity: decrease of approximately 12% (54 study arms)
    • Frequency of sexual activity: odds ratio (OR) = 0.81, 95% confidence interval (CI) 0.72, 0.90 (14 study arms)
    • Number of partners: decrease of approximately 14% (OR = 0.83, 95% CI 0.74, 0.93; 27 study arms)
    • Unprotected sexual activity: decrease of approximately 25% (OR = 0.70, 95% CI 0.60, 0.82; 28 study arms)
    • STIs: decrease of approximately 31% (OR = 0.65, 95% CI 0.47, 0.90; 8 study arms)
    • Use of protection (including use of condoms, oral contraceptives or both): increase of approximately 13% (OR = 1.39, 95% CI 1.19, 1.62; 50 study arms)
      • Condom use: increase of approximately 12% (OR = 1.45, 95% CI 1.20, 1.74; 44 study arms)
  • Results from meta-analyses were also favorable but statistically nonsignificant for the following outcomes.
    • Oral contraceptives: increase of approximately 22% (OR=1.29, 95% CI 0.89, 1.85; 10 study arms)
    • Dual use (use of both condoms and oral contraceptives): increase of approximately 17% (OR=1.21, 95% CI 0.70, 2.12; 4 study arms)
    • Pregnancy: decrease of approximately 11% (OR=0.88, 95% CI 0.60, 1.30; 11 study arms)
  • The review team also examined consistent condom use, a subgroup of the condom use outcome. The results were in the favorable direction, though statistically nonsignificant.
    • Consistent condom use: OR=1.24, 95% CI 0.96, 1.62 (19 study arms)
  • In 17 of the studies, at least one relevant outcome was reported that could not be included in the meta-analyses because of too little information to calculate an odds ratio. The results for these studies were consistent with the results of the meta-analyses.
  • Interventions may be somewhat more effective for boys than girls.

Summary of Economic Evidence

Ten studies qualified for the economic review, including 8 economic evaluations of individual programs. Monetary values are reported in 2008 U.S. dollars.

  • Program costs ranged from $66 to $10,024 per person per year (6 studies).
    • The wide range in costs is the result of variation in program content, number of participants, program duration, and type of program setting.
    • The highest cost programs tended to be multifaceted youth development interventions.
    • The lowest cost programs were school-based and curriculum-based education or involved a large number of participants.
  • The benefit over cost ratio ranged from 2.7 to 3.7. This means that every dollar invested in the CRR programs yielded between $2.70-$3.70 in returns based on savings in healthcare costs related to pregnancies, HIV, and STIs and improvement in income associated with higher educational attainment (2 cost-benefit studies).
    • A separate cost-benefit study that looked at the most expensive program found that the cost of the program exceeded the economic benefits of pregnancy prevention.
  • The net cost per quality adjusted life year (QALY) ranged from $9,000 to $76,000 (2 cost-utility studies).
  • CRR interventions resulted in healthcare savings from prevented pregnancies and STIs that ranged from $5.80 per participant per year for those aged 13-14 years to $338 per participant per year for those aged 18-19 years (1 dissertation).
    • Avoided pregnancies made up 80% of these savings for those aged 13-14 years and more than 95% for those aged 18-19 years.
  • Only 1 of 7 pregnancy prevention programs was found to be cost saving in the state of Washington. This is based on a review of programs requested by the state legislature.


Results suggest that CRR interventions are applicable to:

  • Youth ranging from 10-19 years of age
  • Male only, female only and coed groups
  • Majority African-American, majority White, majority Hispanic and mixed race samples
  • Both virgin and nonvirgin populations
  • School and community settings

Evidence Gaps

Each Community Preventive Services Task Force (Task Force) review identifies critical evidence gaps—areas where information is lacking. Evidence gaps can exist whether or not a recommendation is made. In cases when the Task Force finds insufficient evidence to determine whether an intervention strategy works, evidence gaps encourage researchers and program evaluators to conduct more effectiveness studies. When the Task Force recommends an intervention, evidence gaps highlight missing information that would help users determine if the intervention could meet their particular needs. For example, evidence may be needed to determine where the intervention will work, with which populations, how much it will cost to implement, whether it will provide adequate return on investment, or how users should structure or deliver the intervention to ensure effectiveness. Finally, evidence may be missing for outcomes different from those on which the Task Force recommendation is based.

Identified Evidence Gaps

The following outlines evidence gaps for these group-based behavioral interventions to prevent or reduce the risk of adolescent pregnancy, HIV/AIDS, or other STIs: comprehensive risk reduction, and abstinence education interventions.

Across both reviews, there was no consistent evidence of differential effects on outcomes for any of the 12 critical moderator variables (gender, virginity status, age, race/ethnicity, setting, dosage, focus, deliverer, multicomponent, targeting, study design, and comparison group type). Also, the majority of the studies examined interventions delivered to coed groups and results were not reported by gender. This limits the ability to determine differential effectiveness by gender for comprehensive risk-reduction and abstinence education interventions. This limitation extends to the evaluation of the effectiveness of parental participation as well, since it was an uncommon component in these reviews and often had low participation rates.

More consistent reporting of moderator variables by study authors is needed to clarify which of these (or other characteristics) may maximize the effectiveness of adolescent sexual behavior interventions. In addition, common measures of sexual behavior and standard intervals for follow-up assessments of these outcomes would allow for more comparability across studies and lead to a better determination of the overall public health impact of these interventions.

In terms of economic efficiency, future research is needed to examine how cost– benefit or cost-effectiveness estimates vary depending on age, gender, and risk status of participants. For programs with objectives beyond pregnancy and STI prevention, future research needs to evaluate the full impact of such programs from a societal perspective, including non-health outcomes such as improved employment potential, and higher future earnings of program participants. Finally, for school-based programs, additional research needs to address the impact on school resources where the facilities, staff, or time from the school systems may be used for these programs.

Study Characteristics

Interventions that evaluated STIs were mostly implemented in community settings with adolescents at high-risk for STIs.

Interventions included in this review were:

  • Targeted to adolescents
    • Girls only
    • Boys only
    • Girls and boys together
  • Delivered in group settings in schools or communities
  • Led by adult or peer educators
  • Implemented as single or multicomponent programs
  • Tailored to groups or individuals

Content of these interventions addressed prevention of:

  • HIV and STIs
  • Pregnancy