British scientists have published a study showing that the Delta type of coronavirus can still be transmitted through full vaccinations. This may undermine the possibility of achieving herd immunity. However, vaccination still protects against severe COVID-19 and death from disease.
A study from Oxford University showed that both the Pfizer and BioNTech vaccines and the AstraZeneca vaccine offer slightly less protection from the delta variant than the alpha variant, although this is still a fairly high level of protection. Vaccines continue to protect vaccinated people from hospitalization and death from COVID-19.
Pfizer and AstraZeneca are weaker than Delta
As part of the study, scientists analyzed more than 2.5 million tests taken since December last year on more than 700,000 people. people in Great Britain, which, as shown, makes it the largest study of this kind conducted in real conditions. Since the volunteers participating in the study had regular PCR and antibody tests done, the scientists were able to monitor the changing immunity over time.
The study found that until mid-May, when the alpha variant was the dominant type of coronavirus, vaccines were very effective in preventing infection. However, since the alpha variant has been replaced by a more contagious one delta variableVaccines are less able to contain the virus.
How effective are alternative delta vaccines?
The researchers found that two weeks after the second dose, Pfizer’s vaccine was 85% effective at preventing infection, a significantly better result than the AstraZeneca vaccine, which was 68% effective. But The effectiveness of the Pfizer vaccine fell faster. Three months after the second dose, 75 percent prevented. infection, compared to 61 percent. Protection with AstraZeneca.
The two vaccines seem to work quite differently. But you really have to pay attention to the hospitalization and mortality rates – said the professor. Sarah Walker, lead author of the study.
Elevated level of delta variable in vaccinated patients
The researchers also found that in people who They contracted COVID-19 even though they received two doses of the vaccine, with the delta variant, virus levels can be as high as people who have not been vaccinated. This is the opposite of the alpha variant, where the levels of virus in the vaccine were much lower. This also means that with a delta variable, it is much more difficult – if not impossible to achieve herd immunityj.
We don’t yet know to what extent transmission of infection can occur from people infected with COVID-19 despite being vaccinated. For example, they may have high levels of the virus for a shorter period of time. But the fact that this high viral load indicates that people who have not yet been vaccinated may not be as protected against the delta variant as we had hoped, Prof. Walker.
Source: PAP / Bartłomiej Niedziński (London)
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