Viral Load in Breakthrough Infection After Receiving the Pfizer-BioNTech COVID-19 Vaccine

Lower viral loads were observed in those with positive SARS-CoV-2 tests 12–37 days after the first dose of vaccine compared with unimmunized individuals.

A key objective of mass COVID-19 vaccination is to reduce the viral reproductive number, thereby curbing SARS-CoV-2 spread. Although this is primarily achieved by decreasing the number of individuals susceptible to infection, immunization may also reduce the infectivity of vaccinated persons who experience reinfection. To explore this question, researchers in Israel analyzed positive PCR test results from individuals who had received the Pfizer-BioNTech mRNA vaccine compared with a matched control group of unimmunized persons.

Among 4938 vaccinated and subsequently infected individuals, mean cycle threshold (Ct; inversely related to viral load), was 25 when reinfection occurred 1–11 days after the first dose and 27 when reinfection occurred …

Reviewing Author

Neil M. Ampel, MD

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Editorial BoardsUpToDate

Leadership Positions in Professional SocietiesCoccidioidomycosis Study Group (Past President, Secretary, Treasurer)

Neil M. Ampel, MD

Disclosures

Editorial BoardsUpToDate

Leadership Positions in Professional SocietiesCoccidioidomycosis Study Group (Past President, Secretary, Treasurer)

Viral Load in Breakthrough Infection After Receiving the Pfizer-BioNTech COVID-19 Vaccine

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Reviewing Author