# Zambia CAB-LA cohort of 3,755 people: baseline syphilis 4.57%, incidence 11.76 per 100 person-years

- Published: 2026-11-13 18:21 UTC
- Section: Life & Health › Medicine
- Tags: syphilis in Zambia, long-acting cabotegravir, CAB-LA, HIV pre-exposure prophylaxis, syphilis incidence, retrospective cohort study, STI screening, benzathine penicillin, BMC Public Health
- URL: https://realtech.media/news/rt-792b4fcbac7b55d05e4f98d4_zambia_cab_la/

**A retrospective cohort in Zambia found syphilis among people on injectable cabotegravir for HIV prevention. Two thirds of participants had no documented repeat syphilis test.**

![Zambia CAB-LA cohort of 3,755 people: baseline syphilis 4.57%, incidence 11.76 per 100 person-years](https://realtech.media/media/2026/11/35f1bc9f4db7e8f7.jpg)
*Goleisureintl, Wikimedia Commons, CC BY 4.0*

A retrospective cohort study in Zambia has measured syphilis prevalence and incidence among people receiving long-acting injectable cabotegravir (CAB-LA) for HIV prevention. According to the authors, writing in BMC Public Health, the analysis used routinely collected programmatic data on 3,755 individuals who started CAB-LA across several provinces during the national introduction period, October 2023 to September 2024 [1].

## Baseline prevalence and geography

Valid baseline syphilis results were available for 2,755 participants. Of these, 126 tested reactive, a baseline prevalence of 4.57% (95% CI: 3.85–5.42) [1].

Prevalence differed by province. It was highest in Copperbelt Province (11.36%), followed by Northwestern Province (8.57%) and Western Province (7.27%) [1].

Participants who reported intimate partner violence had a baseline prevalence of 8.70%, against 4.51% among those who did not. Alcohol users had a prevalence of 7.76%, against 4.31% among non-users [1].

## Incident infections and gaps in follow-up testing

Only 1,318 participants had at least one repeat syphilis test during follow-up. The remaining 2,437 (65%) had no documented repeat test [1].

Incident syphilis was assessed among baseline non-reactive participants with at least one repeat test. Among 1,117 such participants, 31 incident infections occurred. This gives a cumulative incidence of 2.78% (95% CI: 1.96–3.91) and an incidence rate of 11.76 per 100 person-years (95% CI: 7.99–16.69) [1].

Southern Province recorded the largest number of incident infections, 21 cases, with an incidence rate of 14.50 per 100 person-years [1].

The authors used Poisson regression with a person-time offset. In the adjusted model, residence in Western Province was associated with higher incident syphilis (adjusted IRR 6.24; 95% CI: 1.02–38.31; p=0.048). Sex, age, depression, intimate partner violence and alcohol use were not statistically significant [1].

The authors conclude that the syphilis burden among CAB-LA users in Zambia remains substantial, with infections concentrated in high-mobility areas. They identify poor follow-up syphilis testing during CAB-LA care as the main programmatic gap. They recommend routine syphilis screening and treatment at every CAB-LA visit, stronger STI monitoring systems, a reliable supply of benzathine penicillin and targeted interventions in high-risk areas [1].

## Sources

1. [BMC Public Health](https://doi.org/10.1186/s12889-026-30223-0)
2. [bioengineer.org](https://bioengineer.org/study-tracks-syphilis-rates-among-injectable-hiv-prevention-users-in-zambia)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-792b4fcbac7b55d05e4f98d4_zambia_cab_la/