Methods
We conducted the sub‐study among Ugandan ODYSSEY participants and compared folate and vitamin B12 between children randomized to dolutegravir‐based ART (DTG) and non‐dolutegravir‐based standard‐of‐care treatment (SOC). Plasma folate was measured at enrolment and week 4 on stored samples; in addition, plasma and red blood cell (RBC) folate and vitamin B12 were assayed at week ≥96 in prospectively collected samples. RBC mean corpuscular volume (MCV) was measured 24‐weekly in all ODYSSEY participants. Samples analysed in the sub‐study were collected between September 2016 and October 2020.