Scientists from the University of Oxford have found that the effectiveness of the Pfizer-BioNTech coronavirus vaccine decreases faster than the AstraZeneca vaccine.
Several studies have demonstrated that Covid vaccines provide significant protection against hospitalization and death risk. However, a new investigation demonstrates that, while being fully vaccinated reduces the likelihood of infection, if infected with Delta, a person can carry comparable virus levels to uninfected people.
The researchers emphasised that the implications for transmission remain unknown.
According to Sarah Walker, an Oxford professor of medical statistics and epidemiology:
We don’t yet know how much transmission can happen from people who get Covid-19 after being vaccinated – for example, they may have high levels of virus for shorter periods of time.
But the fact that they can have high levels of virus suggests that people who aren’t yet vaccinated may not be as protected from the Delta variant as we hoped.
The study demonstrated decreased vaccine performance against Delta compared to the previously dominant Alpha strain.
The research, carried out by Oxford experts in collaboration with the Office for National Statistics and the Department of Health and Social Care, compared the results of approximately 2.6 million nose and throat swabs taken from more than 384,500 adults between December 2020 and mid-May 2021, and more than 811,600 test results from 358,983 adults between mid-May and 1 August 2021 (the period during which Delta dominated).
According to the findings, two doses of the Pfizer/BioNTech vaccine had roughly 15 percent stronger initial efficacy against new infections than two doses of Oxford/AstraZeneca, but the protection fades faster than two doses of Oxford/AstraZeneca.
But the study says that the protection provided by both vaccines is similar four to five months after being fully vaccinated.
“Two doses of Pfizer vaccine have a higher initial efficacy against new strains of coronavirus, but it declines faster than two doses of AstraZeneca2,” the researchers said.
It’s worth noting that the protection against the virus remains the same four to five months after full immunisation.
Scientists also discovered that those who received COVID-19 after completing a full course of vaccination had the same virus burden as those who did not. As a result, the Delta strain appears to be more harmful than the Alpha strain.
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