Alopah learned that a recent study conducted by Oxford University and the British National Bureau of Statistics found that the protective efficacy of PFE. US / biontech (bntx. US) new crown vaccine decreased faster than that of AstraZeneca (Azn. US).
The study was published in preprint form last Thursday local time and has not been officially published in scientific journals. It is generally considered to be the largest study to evaluate and directly compare the real effectiveness of the new crown vaccine.
In this large-scale study, more than 350000 participants aged 18 and over were investigated to evaluate the effectiveness of m-RNA vaccine of Pfizer / biontech and Moderna (mRNA) and adenovirus vector vaccine of AstraZeneca.
The study was conducted in the UK over two time periods: from December 1, 2020 to May 16, 2021, when alpha variant virus was dominant; And from May 17, 2021 to August 1, 2021, when the highly infectious delta mutation dominated.
Since May 17, the efficacy of Pfizer / biontech’s bnt162b2 vaccine in preventing symptomatic diseases within two weeks after the second dose was 93%, while the efficacy of AstraZeneca vaccine was 73%. However, after two weeks, Pfizer’s effectiveness decreased to 84%, while AstraZeneca’s effectiveness remained relatively stable at 71%.
“There are significant differences in immune dynamics between the second dose of Pfizer and AstraZeneca vaccine. Pfizer has higher initial efficacy for new PCR positive, but its protection against high virus load and symptomatic infection decreases faster,” the researchers wrote
The researchers added that the results also showed that the effectiveness of the two vaccines after 4 – 5 months may be similar, but the long-term effects need to be further studied.
Koen Pouwels, a senior researcher at Oxford University who participated in leading the study, said that Pfizer had higher initial effectiveness, but about four and a half months after the second dose of vaccine, Pfizer’s vaccine may be as effective as AstraZeneca’s vaccine in preventing infectious symptoms.
They also found that the single dose efficacy of Moderna new crown vaccine was similar or higher than that of Pfizer / biontech or AstraZeneca, and the results after the second injection of Moderna were not included in the study.
Tomas Hanke, a professor of vaccine immunology at the Jenner Institute of Oxford University, believes that the long-lasting efficacy of AstraZeneca vaccine may be because the spike protein delivered by AstraZeneca can last longer, resulting in a stronger immune response.
“When you deliver RNA, like Pfizer’s vaccine, you deliver a limited number of m-RNA molecules, which will eventually be removed from the system.”
Hanke added: “but when you deliver adenoviruses like AstraZeneca, you deliver a template, and then continue to produce these mRNAs, and then produce spike proteins, so there is no upper limit.”
Unlike the breakthrough m-RNA technology used in Pfizer / biontech and Moderna new crown vaccines, AstraZeneca and Johnson & Johnson (JNJ. US) new crown vaccines are based on viral vectors.
Previously, Israeli research data showed that with the spread of delta mutant virus, the effectiveness of Pfizer / biontech new crown vaccine gradually decreased. By mid July, the effectiveness of preventing infectious symptoms was close to 36%, but it could effectively prevent hospitalization and significantly reduce severe cases.