Zero risk of linked HIV transmission in sero-discordant couples when the HIV-infected partner had viral load (VL)<200 copies/mL (U=U status) was observed in large observational studies. We aimed at estimating the proportion of time in which this status was maintained and identifying factors associated to the risk of losing it among people living with HIV (PLWH) enrolled in a clinical cohort.
We included participants in the ICONA cohort who had reached an established U=U status (VL<=200 copies/mL for >6 months) as of December 2010. The outcome was the number of person days of follow up (PDFU) with a VL>200 copies/ml (cp/ml), relative to the total number of PDFU observed in follow-up. Logistic regression model was used to identify factors independently associated to the risk of losing U=U status. For this analysis, a participant was defined as losing his/her U=U status if he/she spent <90% of his/her PDFU on observation with a VL <=200 cp/mL. The median of VL measurements was 9 (IQR: 4-15).
8,241 PLWH were included in the analysis and contributed 12,670,888 PDFU. Of these, 1,648 (20%) were female, 768 (9%) were people who inject drugs (PWID), 3,786 (46%) men who have sex with men and 3,176 (39%) heterosexuals. Overall, during the entire follow-up, 96.9% of PDFU observed were with a VL<=200 cp/ml. Thus, only 3.1% of PDFU were observed when VL was >200 cp/mL with some evidence for a decrease after 2016. The median time with VL>200 cp/ml was 47.3 days (IQR: 46.3-47.9). Of note, the proportion of PDFU with VL>200 cp/ml was higher than average in females (5.3%), unemployed (5.4%), PWID (4.7%) and in people with>3 previous virological failures (6.3%). At individual level, 617 participants (7.5%) spent <90% of PDFU with a VL<=200 cp/mL and were classified as losing their initial U=U status. Unadjusted and adjusted OR of losing U=U status from fitting the logistic regression model are shown in Table 1.
In our population of PLWH meeting the definition of U=U this status was maintained for 97% of the following 10 years of observation with a trend towards an increase in recent years. These findings reinforce the validity of the U=U message in real world settings. However, we identified subsets of our population, including females and foreign-born, at higher risk of not maintaining the U=U status, for whom greater efforts are needed to reduce these infrequent periods of VL>200 cp/ml.