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. 2022 Sep 18;14(9):2071.
doi: 10.3390/v14092071.

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

Jessica A Plante  1   2 , Rafael R G Machado  2   3 , Brooke M Mitchell  1   2 , Divya P Shinde  1   2 , Jordyn Walker  1   2 , Dionna Scharton  1   2 , Allan McConnell  2 , Nehad Saada  2 , Jianying Liu  2   4 , Bilal Khan  2   5 , Rafael K Campos  2   6 , Bryan A Johnson  2 , Vineet D Menachery  2 , Corri B Levine  7 , Ping Ren  8 , Susan L F McLellan  7 , Kenneth S Plante  1   2 , Scott C Weaver  1   2   6
Affiliations

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

Jessica A Plante et al. Viruses. .

Abstract

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.

Keywords: B.1.617.2; COVID-19; IgA; SARS-CoV-2; breakthrough; delta; vaccination.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
Viral load in NP swabs from asymptomatic Delta variant SARS-CoV-2 infections. (a) SARS-CoV-2 RNA was measured using real time RT-PCR. (b) Infectious SARS-CoV-2 was measured via a microtiter assay. Symbols represent individual subjects, midlines represent the mean, error bars represent the standard deviation, and dashed lines represent the lower limit of the assay. Unvaccinated and vaccinated groups were compared via Mann–Whitney test. ns = p > 0.05, * = p < 0.05.
Figure 2
Figure 2
Anti-SARS-CoV-2 IgA in NP swabs from asymptomatic Delta variant SARS-CoV-2 infections. IgA capable of binding (a) the SARS-CoV-2 S1 protein or (b) the SARS-CoV-2 RBD was measured via flow cytometry. Symbols represent individual subjects, midlines represent the mean, error bars represent the standard deviation, and dashed lines represent the lower limit of the assay. Unvaccinated and vaccinated groups were compared by Mann–Whitney test. ns = p > 0.05, ** = p < 0.01.
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