Follow the Sex: Influence of Network Structure on the Effectiveness and Cost-Effectiveness of Partner Management Strategies for Sexually Transmitted Infection Control

Trajectories of Adherence to Oral Pre-exposure Prophylaxis and Risks of HIV and Sexually Transmitted Infections

Background

Pre-exposure prophylaxis (PrEP) effectiveness is highly dependent on medication adherence, which is associated with differential HIV risks and possibly sexually transmitted infection (STI).

Methods

This retrospective cohort study of PrEP users (01/01/2012-12/31/2021) used the MarketScan database of commercially insured enrollees to examine PrEP adherence trajectory groups' associations with HIV and STI acquisition risks. Distinct PrEP adherence trajectories were identified by group-based trajectory modeling among individuals who used oral PrEP. The primary outcome was HIV acquisition incidence, and secondary was STI rate, compared among trajectory groups. Inverse probability treatment weighting time-varying Cox proportional hazards models assessed HIV acquisition, and Poisson regression models assessed STI.

Results

Among 23 258 oral PrEP users, 4 distinct PrEP adherence patterns were identified: minimal use (10.5% of the cohort), rapidly declining (25.4%), gradually declining (24.3%), and consistently high (39.8%). Compared with the minimal use group, the gradually declining (adjusted hazard ratio [AHR], 0.53; 95% CI, 0.31-0.90) and consistently high (AHR, 0.50; 95% CI, 0.30-0.84) PrEP adherence groups showed decreased HIV incidence risks. Compared with the minimal use group, the rapidly declining (adjusted incidence rate ratio [AIRR], 1.35; 95% CI, 1.07-1.72), gradually declining (AIRR, 1.73; 95% CI, 1.38-2.18), and consistently high (AIRR, 2.06; 95% CI, 1.64-2.58) groups were associated with increased STI risk.

Conclusions

These findings underscore the benefits of continuing and remaining adherent to PrEP and may also inform public health strategies, clinical guidelines, and interventions aimed at maximizing the effectiveness of PrEP in reducing new HIV infections while developing targeted strategies to prevent STIs with PrEP use.

The need for pre-emptive control strategies for mpox in Asia and Oceania

Introduction

The transmission dynamics of the recent mpox outbreak highlights the lack of infrastructure available to rapidly respond to novel STI outbreaks, of which Asia and Oceania remains particularly susceptible. Here, we simulate outbreaks in this setting and propose the use of pre-emptive vaccination within the men who have sex with men (MSM) community before the arrival and establishment of the virus.

Materials and methods

Using data driven heterogeneous sexual contact networks, we simulated outbreaks of mpox in Singapore, Hong Kong, and Sydney. An individual based SEIR compartmental model was used to simulate epidemic trajectories and the impact of different vaccination uptakes was assessed in their ability to avert or suppress outbreaks upon the arrival of mpox within the MSM populations.

Results

The highly dense sexual networks of Singapore and Sydney experience rapid outbreaks, with infection peaks occurring at day 41 and 23 respectively, compared to Hong Kong which occurs at day 77. Across the simulations with no vaccination, 68.2%-89.7% of the MSM community will become infected with mpox across the different cities, over a simulation period of 1 year. By implementing vaccination strategies, the infection rate across the cities can be reduced to as low as 3.1% of the population (range: 3.1%-82.2%) depending on the implementation and uptake of the vaccine. Vaccination is also extremely effective in slowing the start of the epidemic, delaying the epidemic peak by 36-50 days in Hong Kong, or even preventing the outbreak of mpox.

Discussion

With extremely dense and well-connected sexual contact networks, where 65.2%-83.2% of the population are connected to a super-spreader in the different contact networks, pre-emptive or immediate vaccination upon identification of the first case is strongly recommended to help better manage the outbreak of mpox and prevent potential straining of healthcare systems.

Sexually transmitted infections among participants in an HIV PrEP adherence trial

BACKGROUND

HIV PrEP effectiveness is highly dependent on adherence. High STI incidence has been reported among PrEP users. We assessed the relationship between STI incidence (CT, NG, and syphilis) and PrEP adherence.

METHODS

We performed a subanalysis of a controlled, open-label, two-arm, randomized clinical demonstration project of a text-message based adherence intervention. Participants had 48 weeks of follow-up and had STI testing every 12 or 24 weeks. PrEP adherence was measured at week 48 using intracellular tenofovir-diphosphate drug concentrations. We calculated incidence rate ratios for STIs among those adherent as compared with those not adherent to PrEP.

RESULTS

Of the 381 assessed for CT, NG and syphilis at one or more follow-up visits, there were 16 cases of syphilis or 5.0 per 100 person years (95% CI: 2.6, 7.5); 63 cases of NG or 26.3 per 100 person years (95% CI: 19.8, 32.8); and 81 cases of CT or 36.3 per 100 person years (95% CI: 28.4, 44.2). We found no association between adequate PrEP adherence and STI incidence (aIRR: 0.97 95% CI: 0.67, 1.40).

CONCLUSIONS

We found that the incidence of STIs was not significantly different between those adherent to PrEP and those non-adherent. Further research is needed to assess how PrEP use may impact STIs over time.

Exploring and Comparing the Structure of Sexual Networks Affected by Neisseria gonorrhoeae Using Sexual Partner Services Investigation and Genomic Data

BACKGROUND

Sexual networks are difficult to construct because of incomplete sexual partner data. The proximity of people within a network may be inferred from genetically similar infections. We explored genomic data combined with partner services investigation (PSI) data to extend our understanding of sexual networks affected by Neisseria gonorrhoeae (NG).

METHODS

We used 2017-2019 PSI and whole-genome sequencing (WGS) data from 8 jurisdictions participating in Centers for Disease Control and Prevention's Strengthening the US Response to Resistant Gonorrhea (SURRG) project. Clusters were identified from sexual contacts and through genetically similar NG isolates. Sexual mixing patterns were characterized by describing the clusters by the individual's gender and gender of their sex partners.

RESULTS

Our study included 4627 diagnoses of NG infection (81% sequenced), 2455 people received a PSI, 393 people were negative contacts of cases, and 495 were contacts with an unknown NG status. We identified 823 distinct clusters using PSI data combined with WGS data. Of cases that were not linked to any other case using PSI data, 37% were linked when using WGS data. Overall, 40% of PSI cases were allocated to a larger cluster when PSI and WGS data were combined compared with PSI data alone. Mixed clusters containing women, men who report sex with women, and men who report sex with men were common when using the WGS data either alone or in combination with the PSI data.

CONCLUSIONS

Combining PSI and WGS data improves our understanding of sexual network connectivity.