It is now a well-acknowledged fact that COVID-19 vaccines do not offer permanent protection against the virus. Recently the Office for National Statistica in the United Kingdom and the Oxford University conducted a study regarding the efficiency of vaccines in time.
The study discovered that Pfizer’s protection fades quicker than the one of AstraZeneca. The study included 350,000 participants over the age of 18. It was conducted between December 1, 2020, and May 16 2021, focusing on the Alpha variant, and then between May 17, 2021, and August 1, when the Delta strain became the dominant one.
“The dynamics of immunity following second doses differed significantly between BNT162b2 and ChAdOx1, with greater initial effectiveness against new PCR-positives but faster declines in protection against high viral burden and symptomatic infection with BNT162b2,” read the study. It was found that on May 17, the Pfizer vaccine had a 93% effectiveness rate, while the Astra shot only provided 73%. However, Pfizer’s rate dropped to 84% in two weeks, while AstraZeneca was not affected much, dropping only to 71%.
According to the study, more research is required in order to determine the long-term effects. It also found that comparing one dose of Moderna with one dose of Pfizer and the AstraZeneca vaccine did reveal many differences, and they were all quite similar in terms of efficiency.
Professor Tomas Hanke from the Jenner Institute explained the reason why AstraZeneca might be more efficient in the long term: “When you deliver RNA, like the Pfizer vaccine, you deliver a finite number of mRNA molecules which are eventually cleared from the system. But when you deliver the adenovirus, as AstraZeneca does, you deliver a template which then keeps producing these mRNAs that then produce the spike protein, so there’s no ceiling.”