Brazil was strongly affected by the COVID-19 and it is still unknown how it affected sexual and gender minorities'' youth in the country during its burdensome first wave. The aim was to estimate the seroprevalence of antibodies to SARS-CoV-2, and analyze factors associated with the infection among young men who have sex with men (yMSM) and transgender women (yTGW).

A cross-sectional survey nested in PrEP1519, a cohort that investigates the effectiveness of PrEP, and monitors sexual practices among yMSM and yTGW in Salvador, Northeast of Brazil. Serum samples were collected from yMSM and yTGW aged 15-22 years between June-October/2020. IgG and IgM anti-SARS-CoV-2 were detected by chemiluminescence, and data were collected through a socio-behavioral questionnaire. Descriptive, bivariate, and multivariate analyzes with estimated adjusted odds ratios (aOR) and 95% confidence intervals(95%CI) were carried out.

Among the 137-youth participants, the joint prevalence of IgM and IgG was 20.4% (95%CI:14.4- 28.1), and separately: 11.7% (95%CI: 7.2-18.3) for IgM and 16.8% (95%CI:11.3-24.1) for IgG. The rate of self-reporting COVID-19 infection based on symptoms but without tests was 7.6% and based on tests was 5.3%. Most remained sexually active during quarantine measures reporting sex with steady and/or casual partners(67.2%); 19.1% reported never wearing a mask in public venues, and 23.9% believed they could easily recover from COVID-19. Among the participants with positive SARS-CoV-2 antibodies, most remained sexually active during quarantine measures reporting sex with steady and/or casual partners (66.6%); little more than a third reported not wearing a mask in public venues (36%), and believed they could easily recover from COVID-19 (34.4%). The multivariate analysis estimated a statistically significant association between SARS- CoV-2 infection and reports of no use of masks in public venues (aOR=3.11; 95%CI:1.02-9.42), and among those who believed that they could easily recover from COVID-19 (aOR=2.68; 95%CI:1.03-6.95).

The prevalence of SARS-CoV-2 antibodies among yMSM and yTGW was higher than that estimated in seroprevalence surveys conducted in 2020 in the general population of Salvador, indicating a low perception of risk and low adherence to quarantine measures among yMSM and yTGW during the first wave, and likely underreporting of official seroprevalence data for Salvador.