Single-dose COVID-19 vaccines, mostly mRNA-based vaccines, are shown to induce robust antibody responses in individuals who were previously infected with SARS-CoV-2, suggesting the sufficiency of a single dose for those individuals in countries with limited vaccine supply. However, these important data are limited to developed nations. We conducted a prospective longitudinal study among Ethiopian healthcare workers who received a ChAdOx1 nCoV-19 vaccine. We compared the geometric mean titers (GMTs) of the SARS-CoV-2 receptor-binding domain (RBD)-specific IgG antibodies in 39 SARS-CoV-2 naïve participants and 24 participants previously infected with SARS-CoV-2 (P.I.), who received two doses of ChAdOx1 nCoV-19 vaccine across the two post-vaccination time points (at 8 to 12 weeks post single dose and two dose vaccinations). We noted that the GMT (1632.16) in naïve participants at 8–12 weeks post first dose were comparable to the GMT (1674.94) observed in P.I. participants prior to vaccination. Interestingly, P.I. participants had significantly higher antibody titers compared to naïve participants, after both the first (GMT, 4913.50 vs. 1632.16) and second doses (GMT, 9804.60 vs. 6607.30). Taken together, our findings show that a single ChAdOx1 nCoV-19 dose in previously SARS-CoV-2 infected individuals elicits similar, if not higher, antibody responses to those of two-dose-vaccinated naïve individuals.

SARS-CoV-2 and blood-borne viral coinfections are well reported. Nevertheless, little is known regarding the seroprevalence of SARS-CoV-2 and coinfection with blood-borne viruses in hematologic malignancy patients in Ethiopia. We aimed to assess the seroprevalence of SARS-CoV-2 and associated infections with hepatitis B and other viruses among adolescent and adult acute leukemia patients at Tikur Anbessa Specialized Hospital, Addis Ababa, Ethiopia. A cross-sectional study was conducted from July 2020 to June 2021. Blood samples were tested for the presence of anti-SARS-CoV-2, HBV, HCV, and HIV with ELISA kits and occult hepatitis B infection with a real-time polymerase chain reaction assay. Out of a total 110 cases, the SARS-CoV-2 seroprevalence was 35.5%. The prevalence showed a significant increment from July 2020 to the end of June 2021 (p = 0.015). In 22.7% and 2.7% of leukemia cases, HBV and HIV, respectively, were detected. No HCV was identified. The rate of SARS-CoV-2 coinfection with HBV and HIV was 28% (11/39) and 2.6% (1/39), respectively; however, there was no statistically significant association between SARS-CoV-2 seropositivity with HBV and HIV (p > 0.05). There is a need for viral screening in leukemia cases to monitor infections and inform management.