Incidence of SARS-CoV-2 infection in health care workers from Northern Italy based on antibody status: immune protection from secondary infection- A retrospective observational case-controlled study.
Int J Infect Dis
; 109: 199-202, 2021 Aug.
Article
in English
| MEDLINE | ID: covidwho-1385715
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
Full text:
Available
Collection:
International databases
Database:
MEDLINE
Main subject:
Coinfection
/
COVID-19
Type of study:
Experimental Studies
/
Observational study
/
Prognostic study
Topics:
Vaccines
Limits:
Humans
Country/Region as subject:
Europa
Language:
English
Journal:
Int J Infect Dis
Journal subject:
Communicable Diseases
Year:
2021
Document Type:
Article
Affiliation country:
J.IJID.2021.07.003
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