November 23, 2020 – As we approach the end of the year, companies working on COVID-19 vaccines have started rolling out data from their Phase 3 trials – first Pfizer and BioNTech, then Moderna, and now AstraZeneca. In an interim analysis, AstraZeneca and the University of Oxford declared today that their vaccine, AZD1222 (or ChAdOx1 nCoV-19), made up of weakened adenovirus packed with the genetic material of SARS-CoV-2 spike protein, could fight COVID-19 with an average efficacy of 70%.
This number certainly sounds less impressive than Pfizer’s and Moderna’s mRNA vaccines, which showed an efficacy of 95% and 94.5%, respectively. However, this average number has been derived from two different dosing regimens, one which showed 90% efficacy and the other 62%. The difference lies in the level of the dose administered. In the most effective vaccine group, participants were first administered a half dose followed by a full dose, while in the second and less effective vaccine group, volunteers were given two full doses.
“Excitingly, we’ve found that one of our dosing regimens maybe around 90% effective,” said Professor Andrew Pollard, Chief Investigator of the Oxford Vaccine Trial at Oxford. “If this dosing regime is used, more people could be vaccinated with planned vaccine supply.”
The vaccine’s interim analysis comes from pooled data from the Phase 2/3 trials conducted in the UK, COV002, and Brazil, COV003. In total, 11,636 volunteers were analyzed, of which 131 contracted COVID-19. In the cohort that followed the half-dose/full dose regime, 2741 participants, and in two full dose regimen, 8895 participants were analyzed. It is not clear from the statement as to how many volunteers in each of the cohorts developed COVID-19. But the company said all results were statistically significant.
Stable at Fridge Temperatures
One of the major concerns with Moderna and Pfizer’s vaccine is the requirement of low temperatures for storage. The former can stay stable at -20°C for up to 6 months, and at 2 to 8°C for up to 30 days, and at room temperature for up to 24 hours, whereas the latter needs ultra-low temperature for storage. On the other hand, AstraZeneca’s vaccine can be stored and transported at 2 to 8°C for at least six months. This property allows for the transport of the vaccine to other countries with fewer problems.
No Safety Concerns
As for safety, the vaccine led to no hospitalizations or severe COVID-19 in the vaccine arm, but the company remained mum about any adverse event in the placebo arm. AstraZeneca did not specify how the vaccine protected older folks and how it fared in the diverse group of population. However, the trials ongoing in the US, Russia, South Africa, Kenya, and Latin America, as well as in European and Asian countries that include participants over 18 years, will soon reveal whether the vaccine has variable or same efficacy in different age and racial groups. The company previously showed that the vaccine demonstrated a similar robust immune response against the virus across all the adult age groups, including older adults. Although this does not tell whether the older population will be protected, it certainly tells that the vaccine is potent enough to produce an immune response in older adults.
Pascal Soriot, Chief Executive Officer, said: “Today marks an important milestone in our fight against the pandemic. This vaccine’s efficacy and safety confirm that it will be highly effective against COVID-19 and will have an immediate impact on this public health emergency. Furthermore, the vaccine’s simple supply chain and our no-profit pledge and commitment to broad, equitable, and timely access means it will be affordable and globally available, supplying hundreds of millions of doses on approval.”
Good News for Low-Income Countries
With this data, the company will soon submit regulatory paperwork for early approval. It also plans to seek emergency approval from the WHO, which would make the vaccine available to low-income countries sooner. AstraZeneca’s vaccine data is good news for many low-income countries with less sophisticated instruments for storing Pfizer and Moderna’s vaccines. Moreover, it will be available for cheap as the company pledged not to make profits from vaccine sales. This is vital for the protection of the public in countries that cannot afford costly vaccines.
By Ruchi Jhonsa, Ph.D.
Editor: Rajaneesh K. Gopinath, Ph.D.
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