Viruses (Feb 2022)

Influence of the Delta Variant and Vaccination on the SARS-CoV-2 Viral Load

  • Marion Migueres,
  • Chloé Dimeglio,
  • Pauline Trémeaux,
  • Stéphanie Raymond,
  • Sébastien Lhomme,
  • Isabelle Da Silva,
  • Kévin Oliveira Mendes,
  • Florence Abravanel,
  • Marie-Pierre Félicé,
  • Jean-Michel Mansuy,
  • Jacques Izopet

DOI
https://doi.org/10.3390/v14020323
Journal volume & issue
Vol. 14, no. 2
p. 323

Abstract

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Studies comparing SARS-CoV-2 nasopharyngeal (NP) viral load (VL) according to virus variant and host vaccination status have yielded inconsistent results. We conducted a single center prospective study between July and September 2021 at the drive-through testing center of the Toulouse University Hospital. We compared the NP VL of 3775 patients infected by the Delta (n = 3637) and Alpha (n = 138) variants, respectively. Patient’s symptoms and vaccination status (2619 unvaccinated, 636 one dose and 520 two doses) were recorded. SARS-CoV-2 RNA testing and variant screening were assessed by using Thermo Fisher® TaqPath™ COVID-19 and ID solutions® ID™ SARS-CoV-2/VOC evolution Pentaplex assays. Delta SARS-CoV-2 infections were associated with higher VL than Alpha (coef = 0.68; p ≤ 0.01) independently of patient’s vaccination status, symptoms, age and sex. This difference was higher for patients diagnosed late after symptom onset (coef = 0.88; p = 0.01) than for those diagnosed early (coef = 0.43; p = 0.03). Infections in vaccinated patients were associated with lower VL (coef = −0.18; p ≤ 0.01) independently of virus variant, symptom, age and sex. Our results suggest that Delta infections could lead to higher VL and for a longer period compared to Alpha infections. By effectively reducing the NP VL, vaccination could allow for limiting viral spread, even with the Delta variant.

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