Correlates of SARS-CoV-2 anti-RBD IgG antibody titers among persons experiencing homelessness in Los Angeles

ObjectivesPeople experiencing homelessness (PEH) have been especially impacted by the COVID-19 pandemic, likely due to increased vulnerabilities stemming from chronic diseases, substance use, and mental health conditions. DesignA case-control study to assess the presence of antibodies against SARS-CoV-2 among PEH and associations with key variables. SampleA convenience sample of 97 PEH in Skid Row, Los Angeles. MeasurementsA structured questionnaire assessing socio-demographic, mental health, drug and alcohol use, health care access, pandemic stress, and other COVID-19-specific questions. ResultsWe found high anti-receptor binding domain (RBD) IgG titers among five of 15 PEH who reported no prior COVID-19 diagnosis or being vaccinated, suggesting undiagnosed and/or asymptomatic COVID-19. While anti-RBD IgG titers across vaccination categories were not statistically significant (p = .069), participants vaccinated with Janssen had the lowest mean anti-RBD IgG titers. In multivariable analysis, we found negative associations between level of SARS-CoV-2 antibody titers with the Janssen vaccine and depression; thus, a need for integrated care for PEH with depression and COVID-19. ConclusionsFurther research is warranted to confirm the immune response, initial and over time, to SARS-CoV-2 infection and to COVID-19 vaccinations, particularly among PEH whose immune systems may be impacted by multiple health conditions.