Superspreading of SARS-CoV-2 Omicron BA.2.23 among vaccinated Finnish adults : Symptomatic COVID-19 only contracted by those without recent infection

Marianna Riekkinen, Mikael Kajova, Mari Eriksson, Annika Luukkainen, Ville Holmberg, Tuomas Aro, Sari H. Pakkanen, Simo Miettinen, Reetta Montonen, Teemu Smura, Tinja Lääveri, Anu Kantele*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

An outbreak of SARS-CoV-2 was confirmed after an academic party in Helsinki, Finland, in 2022. All 70 guests were requested to fill in follow-up questionnaires; serologic analyses and whole-genome sequencing (WGS) were conducted when possible. Of those participating - all but one with ≥3 vaccine doses - 21/53 (40%) had testconfirmed symptomatic COVID-19: 7% of those with earlier episodes and 76% of those without. Half (11/21) were febrile, but none needed hospitalization. WGS revealed subvariant BA.2.23. Compared to vaccination alone, our data suggest remarkable protection by hybrid immunity against symptomatic infection, particularly in instances of recent infections with homologous variants.

Original languageEnglish
Article numbere113
JournalEpidemiology and Infection
Volume151
Early online date2023
DOIs
Publication statusPublished - 4 Jul 2023
MoE publication typeA1 Journal article-refereed

Keywords

  • COVID-19
  • Hybrid immunity
  • Omicron
  • SARS-CoV-2
  • Superspreading event

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