Alliance for Pandemic Preparedness

February 9, 2021

Decreased SARS-CoV-2 Viral Load Following Vaccination



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[Pre-print, not peer-reviewed] SARS-CoV-2 PCR positive samples collected from persons 12-28 days after receiving the first dose of the Pfizer vaccine had lower viral load concentrations compared to positive samples from non-vaccinated demographically matched persons (based on cycle threshold (Ct) counts to detect genes associated with SARS-CoV-2). The increase in Ct count corresponded to a 4-fold reduction in viral load, which the authors suggest could indicate a lower infectiousness following vaccination.

Levine-Tiefenbrun et al. (Feb 8, 2021). Decreased SARS-CoV-2 Viral Load Following Vaccination. Pre-print downloaded Feb 9 from