"They are completely reducing transfers," said Christopher Byron Brooke at the University of Illinois at Urbana-Champaign. "Vaccinated people transmit the virus in some cases, but the data is clear that the risk of transmission to an infected person is much lower than that of an unvaccinated person."
A recent study found that vaccinated people infected with the delta type had a 63% chance of infecting the uninfected people.
This is slightly lower than the alpha variant, said Brechje de Gier at the National Institute for Public Health and Environment in the Netherlands, who led the study. His team had previously found that alpha-infected vaccinated people had a 73 percent chance of infecting uninvited people.
Important to note, de Gier says, the full effect of vaccines in reducing infections is even higher than 63 percent, because most people who are vaccinated are not infected in the first place.
De Gier and his team used data from a Dutch social media tracking system to determine the so-called second-degree assault - part of the victims' best cases. Then they find out how much this has been reduced by vaccination, fixing things like age.
De Gier says they cannot calculate the total reduction in infection due to vaccination, because they do not know exactly how much the vaccine reduces the risk of infection. But even taking a vaccine reduces the risk of infection by only half, this could mean that vaccines reduce transmission by more than 80 percent in total.
Some have worked full-time. Earlier this year, Ottavia Prunas of Yale University used two different models in data from Israel, where the Pfizer policy was applied. The conclusion of his team was that 89% of all infections.
However, the details used reached March 24, before the delta became stronger. The team is now using the latest data to determine the delta effect, Prunas said.
The perception that vaccines are no longer effective in infection may have emerged in July news reports that vaccinated people infected with the virus “could carry the same virus as others”. Even if this were true, vaccines would still significantly reduce infections by reducing disease in the first place.
In fact, research that removed news reports did not measure the viral load in a person directly but relied on so-called Ct points, the viral RNA level. However, this RNA can be found in viruses that are destroyed by the immune system. "You can measure RNA but it is useless," said Timothy Peto of Oxford University.
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There are now several lines of evidence that Ct scores are not a good measure of a person's viral load. First, the fact that infected people are not vaccinated is very unlikely to infect others. Peto did the same research as de Gier using contact data in England and found similar results.
Second, Peto's team specifically indicated that there was little interaction between Ct scores and infection. “It seems that people who were infected after the vaccination had the same amount of virus in the blood as the one who was not vaccinated. We thought they were also contagious. But it turns out you are not so infected, ”said Peto. “That is very important. People were just not optimistic. ”
However some evidence comes from Brooke's research. His team took samples from 23 people daily after the first test for the virus until the disease was cleared and they performed tests, which included trying to infect cells in the container with samples.
With five out of six people fully vaccinated, no samples were infected, unlike most of the non-vaccinated individuals. The study shows that vaccinated people shed fewer viruses and stop faster than non-vaccinated people, Brooke said.
One of the bad news is that Peto's research shows that the immunizations provided by a vaccine to an infected person decreases over time, about a quarter of three months after the second dose of the vaccine. “This made me confident in the boosters,” he says. "They have to keep going, as we are in the midst of a major outbreak [in the UK]."
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