Determining the impact of vaccination on SARS-CoV-2 RT-PCR cycle threshold values and infectious viral titres
This article has been Reviewed by the following groups
Discuss this preprint
Start a discussion What are Sciety discussions?Listed in
This article is not in any list yet, why not save it to one of your lists.Abstract
Background. As the COVID-19 pandemic continues, efforts to better understand severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral shedding and transmission in both unvaccinated and vaccinated populations remain critical to informing public health policies and vaccine development. The utility of using real time RT-PCR cycle threshold values (C T values) as a proxy for infectious viral litres from individuals infected with SARS-CoV-2 is yet to be fully understood. This retrospective observational cohort study compares quantitative infectious viral litres derived from a focus-forming viral titre assay with SARS-CoV-2 RT-PCR C T values in both unvaccinated and vaccinated individuals infected with the Delta strain.
Methods. Nasopharyngeal swabs positive for SARS-CoV-2 by RT-PCR with a C T value <27 collected from 26 June to 17 October 2021 at the University of Vermont Medical Center Clinical Laboratory for which vaccination records were available were included. Partially vaccinated and individuals <18 years of age were excluded. Infectious viral litres were determined using a micro-focus forming assay under BSL-3 containment.
Results. In total, 119 specimens from 22 unvaccinated and 97 vaccinated individuals met all inclusion criteria and had sufficient residual volume to undergo viral titring. A negative correlation between RT-PCR C T values and viral litres was observed in both unvaccinated and vaccinated groups. No difference in mean C T value or viral titre was detected between vaccinated and unvaccinated groups. Viral litres did not change as a function of time since vaccination.
Conclusions. Our results add to the growing body of knowledge regarding the correlation of SARS-CoV-2 RNA levels and levels of infectious virus. At similar C T values, vaccination does not appear to impact an individual’s potential infectivity when infected with the Delta variant.
Article activity feed
-
-
I am pleased to tell you that your article has now been accepted for publication in Access Microbiology.
-
-
Comments to Author
Dear authors, This manuscript is very well written, and certainly worthy of publication. The data is a useful addition to the 'story' of SARS-CoV-2, and ideally placed in Access Microbiology. I have no major concerns, and only some very minor suggestions. In the introduction, line 58, you mention the arrival of mRNA COVID-19 vaccines, but they were not alone, and were closely followed by other technology-based vaccines (J&J, Oxford/AZ), it might be worth mentioning them here, as they had a role to play also (although perhaps less so in the US). Line 116 looks like there is some track changes left in accidentally? Line 207 - 11.3% received the viral vector vaccine - were these all J&J? Line 326 - 'first state to reach national vaccination...' although its obvious you are talking about the United …
Comments to Author
Dear authors, This manuscript is very well written, and certainly worthy of publication. The data is a useful addition to the 'story' of SARS-CoV-2, and ideally placed in Access Microbiology. I have no major concerns, and only some very minor suggestions. In the introduction, line 58, you mention the arrival of mRNA COVID-19 vaccines, but they were not alone, and were closely followed by other technology-based vaccines (J&J, Oxford/AZ), it might be worth mentioning them here, as they had a role to play also (although perhaps less so in the US). Line 116 looks like there is some track changes left in accidentally? Line 207 - 11.3% received the viral vector vaccine - were these all J&J? Line 326 - 'first state to reach national vaccination...' although its obvious you are talking about the United states when you say 'national', it might be worth clarifying that, for international colleagues.
Please rate the manuscript for methodological rigour
Very good
Please rate the quality of the presentation and structure of the manuscript
Very good
To what extent are the conclusions supported by the data?
Strongly support
Do you have any concerns of possible image manipulation, plagiarism or any other unethical practices?
No
Is there a potential financial or other conflict of interest between yourself and the author(s)?
No
If this manuscript involves human and/or animal work, have the subjects been treated in an ethical manner and the authors complied with the appropriate guidelines?
Yes
-
The work presented is clear and the arguments well formed. This is a study that would be of interest to the field and community.
-
Comments to Author
The manuscript of Peterson et al. analyzed the impact of vaccination on RNA and infectious viral titers in Delta-infected individuals. The main strong point of this study is the quantification of infectious viral titers, which was not extensively done in many published studies. Additionally, the authors confirmed the Ct cut-off for infectious virus isolations, which goes strongly in line with previous studies. The manuscript is clear and well-written. Neither presence of symptoms nor days post-symptom onset were taken into account, the data might be biased. This together with the unequal number of vaccinated and unvaccinated participants could bias the obtained data and thus should be underlined. The study analyzed only Delta infections, the variant which no longer circulating, which decreases the …
Comments to Author
The manuscript of Peterson et al. analyzed the impact of vaccination on RNA and infectious viral titers in Delta-infected individuals. The main strong point of this study is the quantification of infectious viral titers, which was not extensively done in many published studies. Additionally, the authors confirmed the Ct cut-off for infectious virus isolations, which goes strongly in line with previous studies. The manuscript is clear and well-written. Neither presence of symptoms nor days post-symptom onset were taken into account, the data might be biased. This together with the unequal number of vaccinated and unvaccinated participants could bias the obtained data and thus should be underlined. The study analyzed only Delta infections, the variant which no longer circulating, which decreases the importance of this manuscript. Many of the discussed conclusions are no longer applicable to currently circulating variants, and the relevance of the results obtained in this study to currently circulating variants should be discussed. The statistical tests used in the study should be mentioned in the manuscript. The target genes used for the PCR tests should be mentioned. Was Delta a predominantly circulating variant or exclusively circulating variant during the period selected for the study? Line 134: If the samples were stored within four to 4 days of initial testing, the short-term storage conditions should be mentioned. Line 163: Authors mention that only a subset of samples was fully sequenced. Were some variant-specific PCR used to identify the variant? Line 247: "We also compared the relationship between titers and CT values as a function of time since vaccination and observed no differences (Figure 3B)". Statistical tests used and the results of statistical analysis should be mentioned here.
Please rate the manuscript for methodological rigour
Good
Please rate the quality of the presentation and structure of the manuscript
Very good
To what extent are the conclusions supported by the data?
Partially support
Do you have any concerns of possible image manipulation, plagiarism or any other unethical practices?
No
Is there a potential financial or other conflict of interest between yourself and the author(s)?
No
If this manuscript involves human and/or animal work, have the subjects been treated in an ethical manner and the authors complied with the appropriate guidelines?
Yes
-