ABSTRACT
Antibody profiling of vaccinated versus naturally infected individuals is important in evaluating immunity and aiding diagnosis and booster strategies. This study measured antibodies against different antigen targets in healthcare workers (HCW) who have been fully vaccinated with mRNA vaccines, recovered from natural infection, or patients during active infection. All vaccinated individuals were positive for anti-RBD, anti-S1, and anti-S2 antibodies. The median index and interquartile range (IQR) by the Atellica IgG assay were 179 and 140-291 respectively. Among the different antigen targets within the Bioplex assay, the levels of anti-RBD were highest (median >3200 U/mL; IQR >3200 to >3200 U/mL), followed by anti-S1 (median 2132 U/mL; IQR 1649->3200 U/mL) and anti-S2 (median=42 U/mL; IQR=24-76 U/mL). The non-vaccinated recovered cohort showed 90% seropositivity (median index >10; IQR 3.6->10) by Atellica total antibody, 73% by Atellica IgG (median index 3.3; IQR 0.9-9.4), 84% by Bioplex anti-RBD (median 62; IQR 12-269 U/mL), 77% by Bioplex anti-S1 (median 45; IQR 10-83 U/mL), 37% by Bioplex anti-S2 (median 7; IQR 1-12 U/mL), and 79% by Bioplex anti-nucleocapsid (median 69; IQR 20-185U/mL) respectively. The active infection cohort exhibited a similar pattern as the recovered cohort. About 88% and 78% of the recovered and active infection cohort produced both anti-spike and anti-N antibodies with Anti-S1/anti-N ratios ranging from 0.07-16.26. In summary, fully vaccinated individuals demonstrated an average of 50-fold higher antibody levels than naturally infected unvaccinated individuals with immune reactivity strongly towards RBD/S1 and a weak response to S2. The results support vaccination regardless of previous COVID-infection status.
ABSTRACT
ObjectivesFirst responders including firefighters, emergency medical technicians (EMT), paramedics, and police officers are working on the front lines to fight the COVID-19 pandemic and facing a higher risk of infection. This study assessed the seroprevalence among first responders in northeastern Ohio during May-September 2020. MethodsA survey and IgG antibody test against SARS-CoV-2 were offered to University Hospitals Health System affiliated first responder departments. ResultsA total of 3080 first responders with diverse job assignments from more than 400 fire and police departments participated in the study. Among them, 73 (2.4%) were seropositive while only 0.8% had previously positive RT-PCR results. Asymptomatic infection accounts for 46.6% of seropositivity. By occupation, seropositive rates were highest among administration/support staff (3.8%), followed by paramedics (3.0%), EMTs (2.6%), firefighters (2.2%), and police officers (0.8%). Seroprevalence was not associated with self-reported exposure as work exposure rates were: paramedics 48.2%, firefighters 37.1%, EMTs 32.3%, police officers 7.7%, and administration/support staff 4.4%. Self-reported community exposure was strongly correlated with self-reported work exposure rate rather than seroprevalence suggesting a potential impact of risk awareness. Additionally, no significant difference was found among gender or age groups; however, black Americans have a higher positivity rate than other races although they reported lower exposure. ConclusionsDespite the high work-associated exposure rate to SARS-CoV-2 infection, first responders with different roles demonstrated seroprevalence no higher than their administrative/supportive colleagues, which suggests infection control measures are effective in preventing work-related infection.
