PLoS ONE (Jan 2022)

Hygienic behaviors during the COVID-19 pandemic may decrease immunoglobulin G levels: Implications for Kawasaki disease.

  • Hiromi Yamaguchi,
  • Masaaki Hirata,
  • Kuniya Hatakeyama,
  • Ichiro Yamane,
  • Hisashi Endo,
  • Hiroe Okubo,
  • Yoshimi Nishimura,
  • Yoshiro Nagao

DOI
https://doi.org/10.1371/journal.pone.0275295
Journal volume & issue
Vol. 17, no. 9
p. e0275295

Abstract

Read online

BackgroundDue to the coronavirus disease 2019 (COVID-19) pandemic, hygienic behaviors became a new norm since January 2020. The hygiene hypothesis predicts that an excessively hygienic environment may adversely affect human health.ObjectiveWe quantified the effect of COVID-19 on immunological parameters linked to the hygiene hypothesis.MethodsWe examined age-specific levels of total nonspecific immunoglobulin G (IgG) and IgE in individuals who visited Fukuoka Tokushukai Hospital between 2010 and 2021. Pre-COVID (2010-2019) and COVID (2020-2021) periods were compared.ResultsIgG levels steadily decreased throughout Pre-COVID period. IgG levels fell abruptly from the pre-COVID period to the COVID period in all age groups (P = 0.0271, DiscussionHygienic behaviors during the COVID-19 outbreak decreased the chance of infection, which may explain the decreases in IgG levels in children and adults. Neonatal IgG declined, possibly because of the decrease in maternal IgG.ConclusionHygienic behaviors decreased the IgG levels in all age groups, from neonates to adults. This downturn in IgG may lead to vulnerability to infections as well as to KD.