I read Tom's post about not to add fuel to this thread and I fully appreciate his decision.
At the meantime, he did not send pm to me asking me to reduce posting (I also very appreciate that).
I (maybe arrogantly) assume that I can still share some carefully picked non-political, new scientific finding? If this post is better for political forum I will happily transfer it.
Context:
PCR data shows that at least in early days, there is no much difference on the viral load between vaccinated and unvaccinated people, just that vaccinated people have their viral load dropped quicker. Hence there was some doubt on the effectiveness of vaccine pass, being partially quoted by some in this thread (Franco-Paredes, Lancet Infectious Disease).
However, PCR method detects genome copies. It is common for viruses to produce inactive particles with only low percentage infectious. We still use PCR method because 1) it's easier than growing virus in the lab 2) it still reflects how the virus being released. We know since 2020, Covid patient (if not hospitalised) would be less infectious after day 7, even their viral load is still high. It seems that immunity (for natural infection, antibody raises at day 7) can change that infectivity. I assumed vaccine can do similar thing but there is no much evidence, until very recently:
Background Viral load (VL) is one determinant of secondary transmission of SARS-CoV-2. Emergence of variants of concerns (VOC) Alpha and Delta was ascribed, at least partly, to higher VL. Furthermore, with parts of the population vaccinated, knowledge on VL in vaccine breakthrough infections is...
www.medrxiv.org
The Geneva group compared vaccinated and unvaccinated people viral loads (for Delta variant), they found that for PCR (genome copies), indeed at first 3 days the viral loads have little difference, only after that vaccinated people have more significant drop.
However, when checking only infectious particles, vaccinated people have lower infectious viral loads from the beginning.
(Note that it is a log10 chart, it doesn't look huge in chart C but it's actually 5-10 folds difference)
The authors also did statistic analysis to confirm this.
View attachment 23247
That's Delta. How about Omicron? I assume the authors had no time to do the same to Omicron yet, but they did an extra experiment to compare the ratio of genome copies/infectious loads between Delta and Omicron in breakthrough infection cases (all got vaccinated). It shows that Omicron doesn't have a different ratio, which logically means that this infectivity decrease effect should be similar for Omicron.
View attachment 23248
My take:
This is still pending peer review, but if those data is not fake, it looks quite convincing. It shows that PCR viral load is not the only indicator and vaccination is more useful than PCR number shows. Even for Omicron, vaccine not only prevent severe illness and death, but still can contribute in reducing transmission. That means it's not only helping oneself, but also helping others.
www.clinicaltrialsarena.com
