Abstract
Objective: The protection from SARS-CoV-2 infection induced by SARS-CoV-2 anti-S1 and anti-S2 IgG antibody positivity resulting from natural infection was evaluated.
Methods: The frequency of SARS-CoV-2 infection (as determined by virus RNA detection) was evaluated in a group of 1,460 seropositive and a control group of 8,150 seronegative healthcare workers in three Centres of Northern Italy in the period June-November 2020. Neutralizing serum titers were analyzed in seropositive subjects with or without secondary SARS-CoV-2 infection.
Results: During the 6-month survey, 1.78% seropositive subjects developed secondary SARS-CoV-2 infection while 6.63% seronegative controls developed primary infection (odds ratio: 0.26; 95% confidence interval: 0.17-0.38). Secondary infection was associated with low or absent serum neutralizing titer (p<0.01) and was mildly symptomatic in 45.8% cases vs 71.4% symptomatic primary infections (odds ratio: 0.34; 95% confidence interval: 0.16-0.78).
Conclusions: Immunity from natural infection appears protective from secondary infection; therefore, vaccination of seronegative subjects might be prioritized.
Keywords: SARS-CoV-2 infection; immune protection; neutralizing antibody; secondary infection.
【저자키워드】 neutralizing antibody, SARS-COV-2 infection, Secondary infection, immune protection, 【초록키워드】 neutralizing antibody, SARS-CoV-2, vaccination, SARS-COV-2 infection, Infection, Italy, healthcare worker, immune, serum, IgG antibody, Secondary infection, symptomatic, Control, Neutralizing, natural infection, seropositive, seronegative, Protective, Anti-S1, immune protection, Primary infection, Neutralizing titer, Frequency, Odds ratio, determined by, control group, 95% confidence interval, subject, anti-S2, virus RNA, seropositive subjects, serum titer, resulting, analyzed, evaluated, appear, seropositive subject, 【제목키워드】 antibody, Infection, Italy, Health care worker, retrospective,