I emailed the authors regarding this, but thought I'd also put this as a comment:
Figure 3: comparative neutralization responses between variants & wild-type. The serum was drawn at a median of 6 days post breakthrough infection. This isn't enough time for new delta-variant-specific antibodies to form and thus probably reflects the anamnestic memory-b-cell response from original vaccination. I was wondering whether the authors have followed up and evaluated more convalescent sera >2 weeks post-symptoms to see whether it is better able to neutralize delta. It is especially telling to me that the delta neutralization was even worse appearing than the beta neutralization, which would be unexpected unless there was no delta-variant-specific response.
ingokeck • 9 days ago
Dear authors, thanks for putting this interesting data up for discussion. May I propose to change the analysis from Ct values and give median tissue culture infectious dose (TCID50)/mL instead? This would be much more helpful to interpret the data, as it is obvious that for Ct values higher than 25-28 one would need an unlikely big amount of the sample fluid to infect another person.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7454307/ gives the example of Ct 33 corresponding to 0.007 (TCID50)/mL, i.e. 142 ml of the patient sample would be needed to infect 50% of cell culture samples.
It should also be noted that from cell culture experiments it is known that high RNA counts after a few days in unvaccinated patients do not correlate with infectious virus any more and thus cannot be reliably been used to assess the infectiousness. See
https://www.nature.com/articles/s41467-020-20568-4
VirusWar • 10 days ago
Hello, I've got serious doubts about this study :
* performing RT-PCR tests up to 50 Cycle Threshold is not reliable. For exemple virus was found in Caravage (Michelangelo Merisi) body dead in 1610 with 45 CT !
* vaccinated people were on one site and different testing methods were used on each site, so there is a systematic bias
* for plenty of patients, included vaccinated ones, the study reports viral load up to 4 weeks. This is not emphasis in the text but it is quite extraordinary according to what we know currently. Details of viral load data and screening methods should be shared to check this
My Pet Ocelot VirusWar • 9 days ago
You didn't even read the study, they set the Ct to 30.
VirusWar My Pet Ocelot • 7 days ago
Read carefully the study. RT-PCR tests were done with CT up to 45 as you can see on Figure 1 page 16. They said that they also performed genome sequencing when CT<30, which is usual, I saw similar practice in the USA : genome sequencing is only done when viral load is high
