The US immunologist’s statements on the Delta variant are being discussed: “The level of virus in vaccinated who become infected, a rare event, is identical in unvaccinated”
“Now we are dealing with a different virus,” he said Anthony Fauci, chief medical advisor to the White House, referring to the Delta variantof the coronavirus and the decision of the Centers for Disease Control and Prevention (CDC) on the recommendation to wear masks by vaccinates. “This is not the original virus. It has much more efficient capabilities in person-to-person transmission “, added Fauci, reiterating the increased contagiousness of the variant and explained:” The Delta can also infect people who have been vaccinated and these can in turn transmit the virus to others”.
The masks are back
The CDC on Tuesday recommended that people be fully vaccinated return to wearing masks indoors in places where there are high transmission rates (in the US the counties that have over 50 cases per 100,000 residents in a seven-day period). Delta is now the dominant strain in the United States, as in hundreds of other countries in the world (including Italy) and its run does not stop thanks to its ability to infect, estimated between 40 and 60% higher than the Alfa variant, which in turn was 50% more infectious than the original Wuhan strain of SARS-CoV-2. “With about half of Americans not yet vaccinated, there are two pandemics at different speeds in the US,” Fauci reiterated and added that “the majority of people need to get vaccinated. If we reach 85-90% of the vaccinated population, the Delta variant would not have many places to go and would eventually disappear ».
“New scientific evidence”
CDC officials were persuaded to the new order “da new scientific evidence which show that vaccinated people can also be infected e they can carry the virus in large quantities»Writes the New York Times reporting the opinion of Dr. Rochelle P. Walensky, director of the CDC, who added: «In rare occasions, some vaccinated people infected with a Delta variant can be contagious and spread the virus to others.
Finally, Fauci in a video on YouTube summarized the current state of knowledge by recalling that, with complete vaccination, they drop the chance to get infected, of transmit the contagion, to go to the hospital and die.
There are no published studies
How contagious is a vaccine infected with the Delta variant? The variable “contagiousness of a vaccine” does not depend only on the effectiveness of the vaccine received: the effectiveness of the vaccine measures the protection of the individual from getting the virus. Transmission capacity, on the other hand, measures the potential to infect others. On the latter point and the Delta, the data are few and mostly come from the United Kingdom where the Delta has been dominant for a long time. There are no published studies on transmission from one vaccine to another person, but tests (as pointed out by the CDC) are ongoing. So far we have to build on what we know from the other variants.
The effectiveness of the vaccine
The effectiveness of the vaccine in protecting the individual person from getting the virus in Italy it is estimated that 88.5% for vaccinated with 2 doses (source Istituto Superiore di Sanità, ed). The latest English data speak of a protection (with 2 doses) from 65 to 90%. Think of a closed environment with one or more positives: if those present are all vaccinated, 35 out of 100 are infected in the worst case. Vaccines prevent infection and non-infected individuals cannot transmit; therefore, vaccines are also effective in preventing transmission. There protection is high but not total: we know that you can get sick again, but also that Covid disease will be (in almost all cases) mild.
The viral load and contagiousness of positive vaccinates
What does it mean? That even when the vaccine is positive it will transmit fewer viruses?
Yes, it can be understood from the data on infections, which however are empirical. Specific studies on the transmission (usually in the family) between a positive vaccinee and another person are not on the Delta, we wrote that. There are also no studies on viral loads, which are even more difficult to do. There are, however, those that concern the Alpha variant and have shown that the chances that a vaccinated can infect they are very low. the vaccinated people do not get infected in the same way and, in most cases, they have no symptoms. This means that their viral load is low and there is a lower chance of infecting others. If the amount of virus that replicates decreases, its circulation also decreases a lot.
A domestic transmission study in England found that family contacts of cases vaccinated with a single dose had an approximately 40-50% reduced risk of becoming infected. The study was published in the scientific journal New England Journal of Medicine NEJM (one of the most prestigious) coordinated by scientists from the British public service (PHE), but related to the Alfa variant, because it was held until 28 February.
Similar studies have also been conducted in the US and Israel: again on the NEJM, the CDC published a research carried out from 14 December 2020 to 10 April 2021 on 3,975 healthcare professionals. One was encountered 40% lower average viral load in positive vaccinated subjects. The risk offever symptomsat theit was 58% shorter and the shorter duration of illness was 2-3 days. The vaccines attenuated the viral load, the risk of febrile symptoms and the duration of the disease.
A study conducted in February in Israel (not yet published) analyzed people who tested positive for the SARS-CoV-2 test after inoculation with the Pfizer vaccine: viral load was reduced by 4 times for infections that occurred 12-28 days after the first dose of vaccine.
The double shield of the vaccinated: in “entry” and “exit”
These are studies on the Alpha variant, but they lead us to believe that, even considering the greater contagiousness of the Delta, the vaccinated are first of all protected from contagion (as we have seen, between 65 and 90%, ed) and, even if infected, they host a reduced viral load which greatly lowers the chances of infecting them. What are the variables that remain to be calculated? The interactions between these two factors: if I am in a room, vaccinated that I contracted the virus, in any case I will be less infectious than someone who contracted the virus without being vaccinated. More: if I am in an indoor room, my infectious capacity will be practically nil against a vaccinee, who in turn is protected from contagion (more or less depending on the doses he has done and the vaccine he did). Basically there are two shields that protect us. If I meet an unvaccinated person, I will be “not very contagious”, but he will have no protective shields and will be totally susceptible to my weak virus.
July 29, 2021 (change July 29, 2021 | 18:13)
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