Anti-spike antibody responses to SARS-CoV-2 mRNA vaccines in people with schizophrenia and schizoaffective disorder.

IMPORTANCE: Individuals with schizophrenia are at higher risk for severe COVID-19 illness and severe breakthrough infection following vaccination. It is unclear whether immune response to vaccination differs in this population. OBJECTIVE: To assess whether anti-SARS-CoV-2 spike antibody titers after vaccination differ in people with a diagnosis of schizophrenia or schizoaffective disorder (SZ) compared to controls without a psychiatric disorder. DESIGN: This cohort study assessed antibody response following the first and second dose of mRNA vaccines at longitudinal timepoints, up to 7 weeks following the first dose of vaccine. SETTING: A multi-center study including psychiatric healthcare settings in the United States and Europe. PARTICIPANTS: 205 adults with no history of COVID-19 infection, including 106 individuals with SZ and 99 controls without a psychiatric disorder, who received their first dose of SARS-CoV-2 mRNA vaccine between December 20, 2020 and May 27, 2021. MAIN OUTCOMES AND MEASURES: Mean SARS-CoV-2 anti-Spike IgG antibody levels within 7 weeks after the first dose of vaccination. RESULTS: A total of 205 individuals (mean [SD] age, 44.7 [12.0] years; 90 [43.9%] male) were included, of which 106 (51.7%) were diagnosed with SZ. SZ was associated with lower mean log antibody levels (-0.15; 95% CI, -0.27 to -0.03, P = 0.016) after adjusting for age, sex, body mass index, smoking, days since vaccination, and vaccine manufacturer. In secondary analyses of dose-specific responses, SZ was associated with a lower mean log antibody level after the second dose of vaccine (-0.23; 95% CI -0.39 to -0.06, P = 0.006), but not the first dose of vaccine (0.00; 95% CI -0.18- 0.19, P = 0.96). CONCLUSIONS AND RELEVANCE: In this cohort study of individuals with SZ and a control group without psychiatric disorders, SZ was associated with lower SARS-CoV-2 anti-spike antibody levels following 2 doses of SARS-CoV-2 mRNA vaccination. This highlights the need for further studies assessing vaccine immunogenicity in individuals with schizophrenia.