Association Between SARS-CoV-2 Viral Load and COVID-19 Vaccination in 4 Phase 3 Trials

J Infect Dis. 2024 Sep 3:jiae400. doi: 10.1093/infdis/jiae400. Online ahead of print.

Abstract

Coronavirus disease 2019 (COVID-19) vaccines reduce severe disease and mortality and may lessen transmission, measured by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral load (VL). Evaluating vaccine associations in VL at COVID-19 diagnosis in 4 phase 3 randomized, placebo-controlled vaccine trials, July 2020 to July 2021, VL reductions were 2.78 log10 copies/mL (95% confidence interval [CI], 1.38-4.18; n = 60 placebo, 11 vaccine) and 2.12 log10 copies/mL (95% CI, 1.44-2.80; n = 594 placebo, 36 vaccine) for NVX-CoV2373 and mRNA-1273, respectively. Associations were not significant for AZD1222 (0.59 log10 copies/mL; 95% CI, -.19 to 1.36; n = 90 placebo, 78 vaccine) or Ad26.COV2.S (0.23 log10 copies/mL; 95% CI, -.01 to .47; n = 916 placebo, 424 vaccine). Thus, vaccines potentially decreased transmission when ancestral SARS-CoV-2 predominated. Clinical Trials Registration. NCT04470427, NCT04505722, NCT04516746, NCT04611802.

Keywords: COVID-19 transmission; COVID-19 vaccine; SARS-CoV-2 viral load; infectiousness; randomized trial.

Associated data

  • ClinicalTrials.gov/NCT04505722
  • ClinicalTrials.gov/NCT04516746
  • ClinicalTrials.gov/NCT04611802
  • ClinicalTrials.gov/NCT04470427