India variant is four times better able to overcome the protection normally offered by a previous infection
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People who have previously caught COVID-19 are now more likely to be reinfected thanks to the Delta variant, a study has found.
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Laboratory analysis revealed that the variant that originated in India is four times better able to overcome protective antibodies from a previous infection compared with the U.K. Alpha variant.
The study also found that a single dose of either the Pfizer or AstraZeneca vaccines provided just 10 per cent protection against the delta variant.
The variant was already thought to be up to 60 per cent more infectious than the version that swept the U.K. last winter.
However, the findings, published in the journal Nature, help explain why the virus is currently spreading so quickly, particularly among younger adults, who have been less likely to be double-vaccinated.
They are also likely to increase calls for the vaccination of children, given that youngsters can rely less on natural immunity from past infection than previously thought.
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A group of French scientists led by the Institut Pasteur in Paris isolated an infectious Delta strain from a traveller returning from India and examined its sensitivity to antibodies in the blood of COVID-19 convalescent individuals, as well as those who had received a vaccine.
A single dose of either Pfizer or AstraZeneca was “poor or not at all efficient” against both the Delta variant and the Beta (South African) version.
However, administration of a second dose of either vaccine generated a neutralizing response of 95 per cent, although the antibodies were found to be three-to-fivefold less potent against Delta than Alpha.
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Data from the King’s College London/Stanford ZOE COVID-19 symptom study found that of 22,638 new daily symptomatic cases, 11,084 were in people who had received a vaccine.
This is an increase of 85 per cent from the previous week. The figures showed that the positivity rate is significantly higher for those who have received just one dose compared to both — roughly 3.2 per cent compared to one per cent.
According to the King’s study, which relies on up-to-date symptom data entered via its app, there are an estimated 500 cases of long COVID a day among unvaccinated people in the U.K.
Prof. Tim Spector, who leads the project, said: “While it seems that the link between cases and deaths has been fundamentally weakened thanks to an excellent vaccine rollout, we are still seeing a correlation between new cases and long COVID.
“Vaccines reduce the chances of people getting Long Covid, by reducing the risk of seriously debilitating symptoms and also by reducing the chances of an infection lasting more than three months.
“But unfortunately, if new cases continue to increase then many more thousands of people, especially the young, will be affected by long-term symptoms that leave sufferers unable to live life normally.”
Virus antibodies are no match for Delta variant, study shows - National Post
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