Shedding of infectious SARS-CoV-2 despite vaccination
Open Access
- 30 September 2022
- journal article
- research article
- Published by Public Library of Science (PLoS) in PLoS Pathogens
- Vol. 18 (9), e1010876
- https://doi.org/10.1371/journal.ppat.1010876
Abstract
The SARS-CoV-2 Delta Variant of Concern is highly transmissible and contains mutations that confer partial immune escape. The emergence of Delta in North America caused the first surge in COVID-19 cases after SARS-CoV-2 vaccines became widely available. To determine whether individuals infected despite vaccination might be capable of transmitting SARS-CoV-2, we compared RT-PCR cycle threshold (Ct) data from 20,431 test-positive anterior nasal swab specimens from fully vaccinated (n = 9,347) or unvaccinated (n = 11,084) individuals tested at a single commercial laboratory during the interval 28 June– 1 December 2021 when Delta variants were predominant. We observed no significant effect of vaccine status alone on Ct value, nor when controlling for vaccine product or sex. Testing a subset of low-Ct (<25) samples, we detected infectious virus at similar rates, and at similar titers, in specimens from vaccinated and unvaccinated individuals. These data indicate that vaccinated individuals infected with Delta variants are capable of shedding infectious SARS-CoV-2 and could play a role in spreading COVID-19. A pivotal moment in the COVID-19 pandemic in the U.S. occurred during the summer of 2021—after the majority of people were vaccinated against the virus that causes COVID. The paradigm at the time was that infection and transmission after vaccination were rare. After contact tracers noticed an increase in infections after vaccination, we rapidly assembled a team of virologists, epidemiologists, and public health officials to investigate. Our study was conducted in Wisconsin at a time when the Delta variant accounted for almost all new infections. While data related to individual outbreaks and large gatherings were emerging, we examined data from community test sites spread over a wide geographic area in Wisconsin. We found that a large proportion of people with infection despite full vaccination had high levels of virus in their bodies, regardless of sex or the type of vaccine they received. Our study was one of the first to demonstrate the possibility that vaccinated people could play a role in spreading COVID, and helped inform public health policies (such as mask mandates) to cope with new surges in COVID-19 cases.Keywords
Funding Information
- Centers for Disease Control and Prevention (75D30120C09870)
- Centers for Disease Control and Prevention (75D30121C11060)
This publication has 46 references indexed in Scilit:
- Safety and Immunogenicity of Two RNA-Based Covid-19 Vaccine CandidatesThe New England Journal of Medicine, 2020
- An mRNA Vaccine against SARS-CoV-2 — Preliminary ReportThe New England Journal of Medicine, 2020
- Children and Adolescents With SARS-CoV-2 InfectionThe Pediatric Infectious Disease Journal, 2020
- In vivo antiviral host transcriptional response to SARS-CoV-2 by viral load, sex, and agePLoS Biology, 2020
- Age-Related Differences in Nasopharyngeal Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Levels in Patients With Mild to Moderate Coronavirus Disease 2019 (COVID-19)JAMA Pediatrics, 2020
- Duration of infectiousness and correlation with RT-PCR cycle threshold values in cases of COVID-19, England, January to May 2020Eurosurveillance, 2020
- Presymptomatic SARS-CoV-2 Infections and Transmission in a Skilled Nursing FacilityThe New England Journal of Medicine, 2020
- Virological assessment of hospitalized patients with COVID-2019Nature, 2020
- ggplot2Published by Springer Science and Business Media LLC ,2016
- IntroductionPublished by Springer Science and Business Media LLC ,2009