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Seroprevalence and levels of IgG antibodies after COVID-19 infection or vaccination.
Soeorg, Hiie; Jõgi, Piia; Naaber, Paul; Ottas, Aigar; Toompere, Karolin; Lutsar, Irja.
  • Soeorg H; Department of Microbiology, Institute of Biomedicine and Translational Medicine, University of Tartu, Tartu, Estonia.
  • Jõgi P; Children's Clinic of Tartu University Hospital, Tartu, Estonia.
  • Naaber P; Department of Pediatrics, Institute of Clinical Medicine, University of Tartu, Tartu, Estonia.
  • Ottas A; Department of Microbiology, Institute of Biomedicine and Translational Medicine, University of Tartu, Tartu, Estonia.
  • Toompere K; SYNLAB Estonia, Veerenni 53a, Tallinn, Estonia.
  • Lutsar I; Department of Biochemistry, Institute of Biomedicine and Translational Medicine, University of Tartu, Tartu, Estonia.
Infect Dis (Lond) ; 54(1): 63-71, 2022 01.
Article in English | MEDLINE | ID: covidwho-1406440
ABSTRACT

BACKGROUND:

In a country-wide seroprevalence study of COVID-19 in Estonia, we aimed to determine the seroprevalence and the dynamics of IgG against SARS-CoV-2 after vaccination or positive PCR-test.

METHODS:

Leftover blood samples were selected between 8 February and 25 March 2021, by SYNLAB Estonia from all counties and age groups (0-9, 10-19, 20-59, 60-69, 70-79 and 80-100 years) proportionally to the whole Estonian population and tested for IgG against SARS-CoV-2 spike protein receptor-binding domain (anti-S-RBD IgG) using Abbott SARS-CoV-2 IgG II Quant assay. Antibody levels after positive PCR-test or vaccination were described by exponential increase-decrease models.

RESULTS:

According to total of 2517 samples, overall seroprevalence (95% confidence interval [CI]) was 20.1% (18.5-21.7%), similar in all age groups, but varied between counties. If individuals vaccinated with the first dose at least 14 d before antibody measurement were assumed to be seronegative, the overall seroprevalence was 15.8% (14.4-17.3%), 4.0-fold larger than the proportion of PCR-confirmed COVID-19 cases. Of seropositive individuals (n = 506) 194 (38.3%; 33.8-43.1%) had not had positive PCR-test or been vaccinated. According to exponential increase-decrease model, the peak of anti-S-RBD IgG in a 52-year-old (median age of PCR-positive and/or vaccinated individuals) was significantly higher after vaccination compared with positive PCR-test (22,082 (12,897-26,875) vs. 6732 (2321-8243) AU/mL), but half-life was similar (26.5 (6.9-46.1) vs. 38.3 (8.2-68.5) d).

CONCLUSIONS:

One year after the start of COVID-19 pandemic the actual prevalence of infection is still underestimated compared with PCR-confirmed COVID-19 cases. Older compared with younger individuals have lower anti-S-RBD IgG level after vaccination, but similar decline rate.
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Full text: Available Collection: International databases Database: MEDLINE Main subject: Immunoglobulin G / COVID-19 Vaccines / COVID-19 / Antibodies, Viral Type of study: Randomized controlled trials / Risk factors Topics: Vaccines Limits: Adolescent / Adult / Aged / Child / Child, preschool / Humans / Infant / Middle aged / Infant, Newborn / Young adult Country/Region as subject: Europa Language: English Journal: Infect Dis (Lond) Year: 2022 Document Type: Article Affiliation country: 23744235.2021.1974540

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Full text: Available Collection: International databases Database: MEDLINE Main subject: Immunoglobulin G / COVID-19 Vaccines / COVID-19 / Antibodies, Viral Type of study: Randomized controlled trials / Risk factors Topics: Vaccines Limits: Adolescent / Adult / Aged / Child / Child, preschool / Humans / Infant / Middle aged / Infant, Newborn / Young adult Country/Region as subject: Europa Language: English Journal: Infect Dis (Lond) Year: 2022 Document Type: Article Affiliation country: 23744235.2021.1974540