August 11, 2025

Survival of Individuals on Long-Acting Cabotegravir Injection for HIV Pre-Exposure Prophylaxis in Zambia: A Retrospective Cohort Study

Key Points

Survival probabilities decreased over time with significant impact from prior oral PrEP exposure, as shown by a 33% lower discontinuation hazard.
The median survival time was seven months for individuals on CAB LA, with recorded discontinuations showing an incidence rate of 0.129 per person-month.
Retrospective cohort study analyzed secondary data from Electronic Health Records across two districts in Zambia over 10 months.
Findings highlight the need for personalized interventions to sustain adherence, especially for males and those new to PrEP.

Abstract

Background: The HIV epidemic continues to pose a public health challenge in Zambia, despite advances in prevention strategies such as pre-exposure prophylaxis (PrEP). While oral PrEP is effective, daily drug administration remains a significant barrier. Long-acting cabotegravir (CAB LA), an injectable PrEP alternative, addresses this adherence challenge through reduced dosing frequency. This study aimed to assess the survival of individuals on CAB LA for PrEP and identify determinants associated with CAB LA discontinuation. Methods: A retrospective cohort study was conducted using secondary data from the Electronic Health Record on individuals initiating CAB LA between February and September 2024 in Chibombo and Kitwe districts, Zambia. Survival analysis methods, including Kaplan-Meier estimates and Cox proportional hazards regression, were employed to determine survival probabilities and factors associated with discontinuation over a 10-month period. Survival rates between individuals with and without prior oral PrEP exposure were also compared. Results: The survival analysis involved 1,308 individuals contributing 6,386 person-months of follow-up and recorded 823 discontinuations. The median survival time was seven months, with a discontinuation incidence rate of 0.129 per person-month. Survival probabilities decreased over time: 81.6% at one month, 66.6% at three months, 50.6% at five months, 35.5% at seven months, and 26.4% at nine months. Oral PrEP-experienced individuals had a 33% lower hazard of discontinuation, while males had a 20% higher hazard than females. Older age modestly reduced discontinuation risk. Conclusion: CAB LA demonstrates varying survival probabilities over time, with significant predictors of discontinuation identified. These findings underscore the importance of tailored interventions to improve adherence, particularly for males and PrEP-naïve individuals. Key words: HIV prevention, Pre-exposure prophylaxis (PrEP), Long-acting cabotegravir (CAB LA), Discontinuation, Survival analysis.

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