Vaccination Decreases the Infectious Viral Load of Delta Variant SARS-CoV-2 in Asymptomatic Patients

Jessica Plante, Rafael R.G. Machado, Brooke M. Mitchell, Divya P. Shinde, Jordyn Walker, Dionna Scharton, Allan McConnell, Nehad Saada, Jianying Liu, Bilal Khan, Rafael K. Campos, Bryan A. Johnson, Vineet D. Menachery, Corri B. Levine, Ping Ren, Susan L.F. McLellan, Kenneth S. Plante, Scott C. Weaver

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


The Delta variant of SARS-CoV-2 has caused many breakthrough infections in fully vaccinated individuals. While vaccine status did not generally impact the number of viral RNA genome copies in nasopharyngeal swabs of breakthrough patients, as measured by Ct values, it has been previously found to decrease the infectious viral load in symptomatic patients. We quantified the viral RNA, infectious virus, and anti-spike IgA in nasopharyngeal swabs collected from individuals asymptomatically infected with the Delta variant of SARS-CoV-2. Vaccination decreased the infectious viral load, but not the amount of viral RNA. Furthermore, vaccinees with asymptomatic infections had significantly higher levels of anti-spike IgA in their nasal secretions compared to unvaccinated individuals with asymptomatic infections. Thus, vaccination may decrease the transmission risk of Delta, and perhaps other variants, despite not affecting the amount of viral RNA measured in nasopharyngeal swabs.

Original languageEnglish (US)
Article number2071
Issue number9
StatePublished - Sep 2022


  • B.1.617.2
  • COVID-19
  • IgA
  • SARS-CoV-2
  • breakthrough
  • delta
  • vaccination

ASJC Scopus subject areas

  • Infectious Diseases
  • Virology


Dive into the research topics of 'Vaccination Decreases the Infectious Viral Load of Delta Variant SARS-CoV-2 in Asymptomatic Patients'. Together they form a unique fingerprint.

Cite this