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Risk and symptoms of COVID-19 in health professionals according to baseline immune status and booster vaccination during the Delta and Omicron waves in Switzerland-A multicentre cohort study.
Babouee Flury, Baharak; Güsewell, Sabine; Egger, Thomas; Leal, Onicio; Brucher, Angela; Lemmenmeier, Eva; Meier Kleeb, Dorette; Möller, J Carsten; Rieder, Philip; Rütti, Markus; Schmid, Hans-Ruedi; Stocker, Reto; Vuichard-Gysin, Danielle; Wiggli, Benedikt; Besold, Ulrike; McGeer, Allison; Risch, Lorenz; Friedl, Andrée; Schlegel, Matthias; Kuster, Stefan P; Kahlert, Christian R; Kohler, Philipp.
  • Babouee Flury B; Cantonal Hospital St Gallen, Division of Infectious Diseases and Hospital Epidemiology, St Gallen, Switzerland.
  • Güsewell S; Cantonal Hospital St Gallen, Division of Infectious Diseases and Hospital Epidemiology, St Gallen, Switzerland.
  • Egger T; Cantonal Hospital St Gallen, Division of Infectious Diseases and Hospital Epidemiology, St Gallen, Switzerland.
  • Leal O; Epitrack, Recife, Brazil.
  • Brucher A; Department of Economics, University of Zurich, Zurich, Switzerland.
  • Lemmenmeier E; Psychiatry Services of the Canton of St. Gallen (South), St Gallen, Switzerland.
  • Meier Kleeb D; Clienia Littenheid AG, Private Clinic for Psychiatry and Psychotherapy, Littenheid, Switzerland.
  • Möller JC; Kantonsspital Baden, Division of Occupational Health, Baden, Switzerland.
  • Rieder P; Center for Neurological Rehabilitation, Zihlschlacht, Switzerland.
  • Rütti M; Hirslanden Clinic, Zurich, Switzerland.
  • Schmid HR; Fuerstenland Toggenburg Hospital Group, Wil, Switzerland.
  • Stocker R; Kantonsspital Baden, Central Laboratory, Baden, Switzerland.
  • Vuichard-Gysin D; Hirslanden Clinic, Zurich, Switzerland.
  • Wiggli B; Thurgau Hospital Group, Division of Infectious Diseases and Hospital Epidemiology, Muensterlingen, Switzerland.
  • Besold U; Kantonsspital Baden, Division of Infectious Diseases and Hospital Epidemiology, Baden, Switzerland.
  • McGeer A; Geriatric Clinic St. Gallen, St. Gallen, Switzerland.
  • Risch L; Sinai Health System, Toronto, Canada.
  • Friedl A; Labormedizinisches Zentrum Dr Risch Ostschweiz AG, Buchs, Switzerland.
  • Schlegel M; Private Universität im Fürstentum Liechtenstein, Triesen, Liechtenstein.
  • Kuster SP; Center of Laboratory Medicine, University Institute of Clinical Chemistry, University of Bern, Inselspital, Bern, Switzerland.
  • Kahlert CR; Kantonsspital Baden, Division of Infectious Diseases and Hospital Epidemiology, Baden, Switzerland.
  • Kohler P; Cantonal Hospital St Gallen, Division of Infectious Diseases and Hospital Epidemiology, St Gallen, Switzerland.
PLoS Med ; 19(11): e1004125, 2022 Nov.
Article in English | MEDLINE | ID: covidwho-2109279
ABSTRACT

BACKGROUND:

Knowledge about protection conferred by previous Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection and/or vaccination against emerging viral variants allows clinicians, epidemiologists, and health authorities to predict and reduce the future Coronavirus Disease 2019 (COVID-19) burden. We investigated the risk and symptoms of SARS-CoV-2 (re)infection and vaccine breakthrough infection during the Delta and Omicron waves, depending on baseline immune status and subsequent vaccinations. METHODS AND

FINDINGS:

In this prospective, multicentre cohort performed between August 2020 and March 2022, we recruited hospital employees from ten acute/nonacute healthcare networks in Eastern/Northern Switzerland. We determined immune status in September 2021 based on serology and previous SARS-CoV-2 infections/vaccinations Group N (no immunity); Group V (twice vaccinated, uninfected); Group I (infected, unvaccinated); Group H (hybrid infected and ≥1 vaccination). Date and symptoms of (re)infections and subsequent (booster) vaccinations were recorded until March 2022. We compared the time to positive SARS-CoV-2 swab and number of symptoms according to immune status, viral variant (i.e., Delta-dominant before December 27, 2021; Omicron-dominant on/after this date), and subsequent vaccinations, adjusting for exposure/behavior variables. Among 2,595 participants (median follow-up 171 days), we observed 764 (29%) (re)infections, thereof 591 during the Omicron period. Compared to group N, the hazard ratio (HR) for (re)infection was 0.33 (95% confidence interval [CI] 0.22 to 0.50, p < 0.001) for V, 0.25 (95% CI 0.11 to 0.57, p = 0.001) for I, and 0.04 (95% CI 0.02 to 0.10, p < 0.001) for H in the Delta period. HRs substantially increased during the Omicron period for all groups; in multivariable analyses, only belonging to group H was associated with protection (adjusted HR [aHR] 0.52, 95% CI 0.35 to 0.77, p = 0.001); booster vaccination was associated with reduction of breakthrough infection risk in groups V (aHR 0.68, 95% CI 0.54 to 0.85, p = 0.001) and H (aHR 0.67, 95% CI 0.45 to 1.00, p = 0.048), largely observed in the early Omicron period. Group H (versus N, risk ratio (RR) 0.80, 95% CI 0.66 to 0.97, p = 0.021) and participants with booster vaccination (versus nonboosted, RR 0.79, 95% CI 0.71 to 0.88, p < 0.001) reported less symptoms during infection. Important limitations are that SARS-CoV-2 swab results were self-reported and that results on viral variants were inferred from the predominating strain circulating in the community at that time, rather than sequencing.

CONCLUSIONS:

Our data suggest that hybrid immunity and booster vaccination are associated with a reduced risk and reduced symptom number of SARS-CoV-2 infection during Delta- and Omicron-dominant periods. For previously noninfected individuals, booster vaccination might reduce the risk of symptomatic Omicron infection, although this benefit seems to wane over time.
Subject(s)

Full text: Available Collection: International databases Database: MEDLINE Main subject: Viral Vaccines / COVID-19 Type of study: Cohort study / Experimental Studies / Observational study / Prognostic study / Randomized controlled trials Topics: Vaccines / Variants Limits: Humans Country/Region as subject: Europa Language: English Journal: PLoS Med Journal subject: Medicine Year: 2022 Document Type: Article Affiliation country: Journal.pmed.1004125

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Full text: Available Collection: International databases Database: MEDLINE Main subject: Viral Vaccines / COVID-19 Type of study: Cohort study / Experimental Studies / Observational study / Prognostic study / Randomized controlled trials Topics: Vaccines / Variants Limits: Humans Country/Region as subject: Europa Language: English Journal: PLoS Med Journal subject: Medicine Year: 2022 Document Type: Article Affiliation country: Journal.pmed.1004125