Oxford University Study: Pfizer/BioNTech COVID-19 vaccine protection dropped faster than AstraZeneca’s
A recent study conducted by the Oxford University and the Office for National Statistics in the U.K. found that the protection gained from Pfizer (NYSE:PFE)/BioNTech (NASDAQ:BNTX) COVID-19 vaccine dropped faster than that from AstraZeneca (NASDAQ:AZN).
- Released on Thursday as a pre-print, the study was the largest to evaluate and directly compare the real-world effectiveness of the vaccines. It did not involve the scientists who pioneered the development of Astra’s COVID-19 vaccine, named ChAdOx1.
- With the participation of over 350,000 individuals aged 18 years and older, the COVID-19 Infection Survey assessed the effectiveness of messenger-RNA vaccines from Pfizer (PFE)/BioNTech (BNTX) and Moderna (NASDAQ:MRNA) along with adenoviral vector-based vaccine from AstraZeneca (AZN).
- The study was conducted in the U.K. across two time periods: between December 01, 2020, and May 16, 2021, when the Alpha variant was dominant, and between May 17, 2021, and August 01, 2021, when the highly contagious Delta variant replaced Alpha as the dominant strain there.
- From May 17, Pfizer/BioNTech shot, named BNT162b2 had 93% effectiveness against the symptomatic disease within two weeks after the second dose, compared to 73% of Astra’s COVID-19 shot. However, beyond two weeks, its effectiveness dropped to 84% while that of AstraZeneca (AZN) held relatively steady at 71%.
- “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,” the authors of the study wrote.
- Results also indicate that the effectiveness of the two vaccines would be similar after four-five months, however, the long-term effects need to be further studied, the researchers added.
- They also found that a single dose of Moderna’s COVID-19 vaccine had a similar or greater level of efficacy compared to a single dose from Pfizer/BioNTech or AstraZeneca vaccines. The study did not include the results following Moderna’s second shot.
- Tomas Hanke, professor of vaccine immunology at Oxford’s Jenner Institute, suggested that the lasting efficacy of the AstraZeneca vaccine could be due to its delivery of spike proteins which could last for a longer time, that can generate a stronger immune response.
- “When you deliver RNA, like the Pfizer vaccine, you deliver a finite number of mRNA molecules which are eventually cleared from the system,” Financial Times quoted Hanke as saying.
- The messenger-RNA vaccine platform uses lipid nanoparticles to deliver mRNA molecules that can then encode COVID-19 spike proteins in human cells to induce immunity without the actual infection.
- “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,” Hanke added.
- Both COVID-19 vaccines from AstraZeneca and Johnson & Johnson & Johnson are based on viral vectors, unlike the breakthrough mRNA technology used in Pfizer/BioNTech and Moderna shots.
- Previously, data from Israel indicated that with the prevalence of Delta variant, the effectiveness of Pfizer/BioNTech COVID-19 vaccine gradually declined, approaching 36% in preventing infections by mid-July.
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