A longitudinal study of SARS-CoV-2 antibody response in a subset of United States blood donors


 
 
 Blood donors were tested for antibodies to SARS-CoV-2; resulting antibody levels were monitored over time.
 
 
 
 Donors reactive to anti-SARS-CoV-2 spike protein (S1-total antibodies) participated in a follow-up study of 18 months.Testing for nucleocapsid antibodies distinguished between vaccination and infection. Vaccination and symptom information were collected for anti-S1-reactive donors by completing a survey.
 
 
 
 The majority of 249 followed donors were over 60 years old (54%), Caucasian (90%), and female (58%); 83% had not been vaccinated at enrollment, but by study completion, only 29% remained nonvaccinated. Of the 210 (84%) anti-N-reactive donors, 138 (66%) reported vaccination, while 37 (95%) of donors vaccinated and anti-N negative at enrollment remained uninfected. Vaccinated (2 doses) and infected donors showed a steady increase in anti-S1 that increased markedly for vaccinated donors following a booster and infected donors after vaccination (slightly higher for those with hybrid immunity), while anti-N levels declined. Most surveyed nonvaccinated donors (65%) reported symptoms, while 85% of vaccinated donors were asymptomatic. A COVID-19 diagnosis was reported by 48 (31%) nonvaccinated and three (8%) vaccinated donors.Of asymptomatic donors, 38% never tested diagnostically for COVID-19, and 35% tested negative, suggesting an absence of knowledge of the infection.
 
 
 
 Healthy blood donors were vaccinated at high rates and remained mostly asymptomatic and noninfected, while about two-thirds of infected donors reported symptoms. Anti-S1 levels increased while anti-N decreased over 18 months but remained comparable between vaccinated and hybrid immune individuals with dramatic anti-S1 increases following vaccination or boosting.
