AstraZeneca Announces AZD1222 Vaccine Shows 76% Efficacy with Single Dose and Up to 82% with Extended Dosing Interval
AstraZeneca
Biopharmaceutical Manufacturer
University of Oxford
The University of Oxford (commonly referred to as "Oxford") is a public research university located in Oxford, England. Operating under a collegiate federal system, it is collectively known with the University of Cambridge as "Oxbridge." Together with the University of Cambridge, University College London, Imperial College London, and the London School of Economics and Political Science, it forms the "G5 Super Elite Universities."While the exact founding date of the University of Oxford is lost to history, archival records clearly indicate that teaching commenced as early as 1096. The university experienced rapid development after receiving substantial support from the English royal family in 1167. It is the oldest university in the English-speaking world and the second-oldest surviving higher education institution globally. The University of Oxford holds prestigious academic standing and extensive influence in fields such as mathematics, physics, medicine, law, and business, and is widely recognized as one of the world’s leading higher education institutions. In the 2017–18 Times Higher Education World University Rankings, Oxford ranked first worldwide; in the Academic Ranking of World Universities (ARWU), it ranked seventh globally.On December 18, 2018, the "2018 World Brand 500" list, compiled by the World Brand Lab, was released, with the University of Oxford ranked 99th.
European Medicines Agency
The European Medicines Agency (EMA) is a decentralized agency of the European Union (EU), located in London. It began operations in 1995. The agency is responsible for the scientific evaluation, supervision, and safety monitoring of medicines developed by pharmaceutical companies for use in the EU. By ensuring that all medicines available on the EU market are safe, effective, and of high quality, the EMA protects public and animal health in the 28 EU Member States and countries of the European Economic Area.
On February 3 (local time), AstraZeneca announced that the COVID-19 vaccine (AZD1222), jointly developed with the University of Oxford, may have the potential to curb the spread of SARS-CoV-2. A single dose of AZD1222 demonstrated 76% efficacy, while vaccine efficacy reached 82% when the interval between two doses exceeded 12 weeks.
Just days before the announcement, the vaccine had received emergency approval from the European Medicines Agency (EMA), becoming the third COVID-19 vaccine authorized by the EMA for use in individuals aged 18 and older.
AZD1222 is a COVID-19 vaccine based on a replication-deficient chimpanzee adenovirus vector. Upon vaccination, it induces the expression of the surface spike protein, thereby stimulating the immune system to attack SARS-CoV-2.
In the latest report, researchers published further data analysis of the AZD1222 vaccine trial as a preprint in The Lancet. A study of 332 symptomatic COVID-19 cases accumulated among 17,177 participants found that a single dose of the vaccine provided effective protection against SARS-CoV-2 infection starting 22 days post-vaccination, with this protective effect lasting through day 90 and achieving an efficacy of 76%.
Moreover, the trial results revealed a significant impact of the prime-boost interval on vaccine efficacy. The study found that vaccine protective efficacy increased with longer intervals between the two doses; specifically, when comparing a 6-week interval to a 12-week interval, protective efficacy rose from 54.9% to 82.4%. This suggests that SARS-CoV-2 transmission may be associated with the interval between the two vaccine doses.
As early as late last year, the University of Oxford and AstraZeneca conducted a study based on 131 symptomatic COVID-19 cases among 11,636 participants, and published the interim results of the Phase III clinical trial of the vaccine in The Lancet. The data showed that AZD1222 had an efficacy of 70.4% against COVID-19. This new study further confirmed the interim results, demonstrating 100% efficacy of two doses of the vaccine in preventing severe COVID-19.
Despite the rather optimistic experimental results, we must not be blindly confident in the face of the cunning SARS-CoV-2. Recently, an article published in JAMA titled “SARS-CoV-2 Vaccines and the Growing Threat of Viral Variants” questioned the strategy of “extending the vaccination interval”: Will extending the time between two doses be threatened by SARS-CoV-2 variants?
Researchers have proposed that when viruses are subjected to stress that restricts their replication capacity, they find ways to evade such pressure and restore effective reproductive capability, leading to the phenomenon of “escape mutations.”
In light of this situation, researchers have offered several recommendations: Given the global spread of new SARS-CoV-2 variants, it is imperative to immediately isolate and characterize SARS-CoV-2 from vaccinated individuals who still contract COVID-19, as this may represent the first sign of vaccine resistance. Secondly, a surveillance system should be established to rapidly identify emerging viral mutations, enabling timely adjustments to COVID-19 vaccines to maintain their efficacy against new variants. Furthermore, establishing a serum biobank would add significant value. Meanwhile, preventive measures such as wearing masks, frequent handwashing, and maintaining physical distancing remain essential.
Amid the pandemic, the emergence of vaccines has brought new hope. Recently, Moderna’s COVID-19 vaccine successfully passed Phase 3 clinical trials, becoming one of the leading candidate vaccines. There are also indications that this vaccine can curb the transmission of SARS-CoV-2, with clinical results showing a 60% reduction in the proportion of asymptomatic COVID-19 cases. Consequently, the vaccine has received emergency approval in the UK and is expected to be administered this spring.
References:
[1]https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)32661-1/fulltext
[2]https://www.livescience.com/astrazeneca-oxford-coronavirus-vaccine-cuts-transmission.html
[3]https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3777268
[4]https://jamanetwork.com/journals/jama/fullarticle/2776039