Evaluating SARS-CoV-2 Seroconversion Following Relieve of Confinement Measures

Area of Science:

• Immunology
• Epidemiology
• Public Health

Background:

• Seroprevalence studies are vital for assessing SARS-CoV-2 exposure and evaluating public health interventions.
• Portugal implemented university closures on March 16th, 2020, with limited initial SARS-CoV-2 cases.
• NOVA University of Lisbon partially resumed on-site work on May 25th, 2020.

Purpose of the Study:

• To estimate SARS-CoV-2 exposure prevalence among university collaborators.
• To measure the efficiency of confinement measures through serological surveillance.
• To assess the prevalence of asymptomatic or paucisymptomatic SARS-CoV-2 infections.

Main Methods:

• Validated a SARS-CoV-2 ELISA assay using a full-length spike protein.
• Screened 1,636 NOVA University of Lisbon collaborators for SARS-CoV-2 specific IgA and IgG antibodies.
• Conducted screening 3-4 weeks after easing confinement measures (June 15th-30th).

Main Results:

• Detected spike-specific IgG antibodies in 50 out of 1,636 participants (3.0%).
• No participants tested positive for anti-spike IgA antibodies.
• Essential workers exhibited a 2-fold increase in viral exposure compared to non-essential workers.

Conclusions:

• The study provides seroprevalence data for asymptomatic/paucisymptomatic SARS-CoV-2 infections.
• Findings suggest differential viral exposure risks between essential and non-essential workers.
• Further serological surveys are recommended for a comprehensive understanding of confinement measure impact.