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. 2011 Apr 15;56(5):453-9.
doi: 10.1097/QAI.0b013e3182118fa3.

Risk Factors for HIV-1 Infection in a Longitudinal, Prospective Cohort of Adults From the Mbeya Region, Tanzania

Free PMC article

Risk Factors for HIV-1 Infection in a Longitudinal, Prospective Cohort of Adults From the Mbeya Region, Tanzania

Steffen Geis et al. J Acquir Immune Defic Syndr. .
Free PMC article


Background: To control the global HIV epidemic, targeted interventions to reduce the incidence of HIV infections are urgently needed until an effective HIV vaccine is available. This study describes HIV-1 incidence and associated risk factors in a general population cohort of adults from Mbeya region, Tanzania, who participated in a vaccine preparedness study.

Methods: We conducted a closed prospective cohort study with 6-monthly follow-up from 2002 to 2006 enrolling adults from the general population. HIV-1 incidence and risk factors for HIV-1 acquisition were analyzed using Cox regression.

Results: We observed 2578 seronegative participants for a mean period of 3.06 person years (PY) (7471 PY in total). Overall HIV-1 incidence was 1.35 per 100 PY (95% confidence interval [CI], 1.10-1.64/100 PY). The highest overall HIV-1 incidence was found in females from Itende village (1.55 per 100 PY; 95% CI, 0.99-2.30/100 PY); the highest age-specific incidence was observed in semiurban males aged 30 to 34 years (2.75 per 100 PY; 95% CI, 0.75-7.04). HIV-1 acquisition was independently associated with female gender (hazard ratio [HR], 1.64; 95% CI, 1.05-2.57), younger age at enrollment (age 18-19 versus 35-39 years: HR, 0.29; 95% CI, 0.11-0.75), alcohol consumption (almost daily versus none: HR, 2.01; 95% CI, 1.00-4.07), education level (secondary school versus none: HR, 0.39; 95% CI, 0.17-0.89), and number of lifetime sex partners (more than five versus one: HR, 2.22; 95% CI, 1.13-4.36).

Conclusions: A high incidence of HIV was observed in this cohort, and incident infection was strongly associated with young age, alcohol consumption, low school education level, and number of sex partners. Targeted interventions are needed to address the elevated risk associated with these factors.


Figure 1
Figure 1. HIV-1 incidence
Incidence of HIV seroconversion (point estimates) for males and females, stratified by recruitment site and age.
Figure 2
Figure 2. Kaplan-Meier cumulative Rates of Infection
The first follow-up visit was held approximately 6 months (±2 months) after enrolment, the last one after 46 months. The graph shows probability of HIV-1 infection (solid line) and 95% confidence intervals (shaded gray). Numbers indicate the number at risk for each study year and the number of seroconversions.

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