On Monday, pharmaceutical giant AstraZeneca and its partner Oxford University released preliminary results from its phase 3 Covid-19 vaccine trials, which found that the company’s vaccine, which uses a genetically modified cold virus, is up to 90% effective. This makes AstraZeneca the third to announce preliminary data from its phase 3 trials, after Moderna and Pfizer released results from their phase 3 trials earlier this month. Both Moderna and Pfizer, whose vaccines use an mRNA platform, found their vaccines to be about 95% effective. The AstraZeneca/Oxford vaccine showed a somewhat lower efficacy, but is less expensive and poses fewer issues involved in distribution and administration.
“Today marks an important milestone in our fight against the pandemic,” AstraZeneca CEO Pascal Soriot said in a statement. “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.”
Here’s what you need to know.
This vaccine’s technology is different from Pfizer and Moderna’s
The AstraZeneca-Oxford vaccine is a chimpanzee adenovirus-vectored vaccine. This means that the company took a virus that normally infects chimpanzees, and genetically modified to avoid any possible disease consequences in people. This modified virus carries a portion of the Covid-19 coronavirus called the “spike protein.” When the vaccine is delivered into human cells, it triggers an immune response against the spike protein, producing antibodies and memory cells that will be able to recognize the virus that causes Covid-19.
Adenovirus-vectored vaccines have been in development for a long time, in particular against malaria, HIV, and Ebola. But no adenovirus vaccine has ever been approved for human use in the U.S. Some adenovirus vaccines in past trials have been simply ineffective, while others have been attacked by the body’s immune system (human adenoviruses can cause the common cold, so some people already have antibodies to these viruses). Researchers behind the Covid-19 vaccine are working around this problem by using a chimpanzee virus that few humans have antibodies to. Previous trials have shown that their vaccine triggers an immune response to Covid-19.
Other companies are also working on adenovirus vaccines against Covid-19, including Johnson & Johnson, whose vaccine is currently in clinical trials with preliminary results expected in early 2021. China-based CanSino Biologists is also developing an adenovirus virus, as is NantKwest, the biotech company founded by billionaire Patrick Soon-Shiong.
Preliminary results suggest that this adenovirus vaccine can be effective
The preliminary data released on Monday studied two different ways to administer the vaccine. In one group, patients were given a smaller initial dose of the vaccine (or placebo), then a larger dose as a booster one month later. In the second group, patients were given the same dose both initially and as a booster one month later. In the first group, the interim data analysis found that the vaccine was about 90% effective at preventing Covid-19. Paradoxically, the second group, which had the larger initial dose, showed that the vaccine was only about 62% effective.
It’s not entirely clear why the smaller initial dose produces better results, though scientists in the field have suggested several ideas. First is that the difference may just be a statistical artifact – a consequence of the fact that this is an interim data analysis, and that once the final results are in the difference may be smaller. The second possibility is that the smaller initial dose may stimulate “memory cells” in the immune system, priming the body to produce antibodies in greater quantities when the second dose is administered. The third possibility is that the larger initial dose may be causing the body to develop antibodies against the vaccine itself, blunting the impact of the booster shot. More study will be needed to answer this question.
That said, these interim results are in line with a peer-reviewed study published in medical journal Lancet last week, which found that the AstraZeneca vaccine bolstered the immune response to Covid-19 in older adults, who are most at risk of developing severe versions of the disease. So far, no serious safety concerns have emerged from the clinical trials, which were conducted with over 23,000 people.
The vaccine still needs to be approved by regulatory authorities
The next step for AstraZeneca is to have its vaccine approved by regulators. This week, the company has said it intends to provide its data to regulators in the United Kingdom, the European Union and the United States for emergency authorization to begin administering the vaccine. It’s additionally seeking an emergency authorization from the World Health Organization to administer the vaccine in low-income countries.
No adenovirus vector vaccine has yet been approved for use in the United States, though several have completed phase 2 studies with adenovirus vaccines against other diseases. A few have been approved globally, including CanSino’s adenovirus vaccine against Ebola, which was authorized for emergency use in China in 2017. The Sputnik V vaccine against Covid-19, developed by the Gamaleya Research Institute of Epidemiology and Microbiology, has been approved in Russia. However, there have been serious questions about how effective that vaccine is, especially after data published in The Lancet sparked serious skepticism from scientists around the world in September.
“We can only hope that together with Pfizer and also Moderna and also Astrazeneca, we will manufacture enough doses.”
AstraZeneca and Oxford received over $1 billion from the U.S. government to fund vaccine development
In May, the U.S. Biomedical Advanced Research and Development Authority (BARDA) provided AstraZeneca and Oxford more than $1 billion in funding to develop this Covid-19 vaccine. AstraZeneca also agreed to supply the U.S. with at least 400 million doses of the vaccine if it is approved. Additionally, in June they partnered with the Center For Epidemic Preparedness Innovations, a global partnership between public and private entities, to scale up manufacturing of the vaccine. Also in June, the company reached an agreement with Europe’s Inclusive Vaccine’s Alliance to provide 400 million vaccine doses at cost, with no profit, during the duration of the pandemic.
If approved, the vaccine should be generally available in 2021
Once regulatory bodies authorize use of the vaccine, AstraZeneca will begin manufacturing doses, having struck arrangements with a number of different organizations to make it quickly. In a statement released Monday, the company said it could produce up to 3 billion doses of the vaccine in 2021.
AstraZeneca’s vaccine can be stored at higher temperatures than Pfizer’s or Moderna’s
Both Pfizer and Moderna’s vaccines require long-term storage at low temperatures, Pfizer’s at -94° Fahrenheit and Moderna’s at -4° Fahrenheit, though both appear to be able to tolerate being refrigerated for short periods of time at higher temperature. These storage requirements may pose potential roadblocks in areas that lack access to the equipment needed to maintain those temperatures. By contrast, AstraZeneca’s vaccine can be transported and stored at the same temperatures you might find in a normal refrigerator – between about 36° and 46° Fahrenheit for as long as six months.
Other vaccines will be needed to ensure global coverage
Even if AstraZeneca can manufacture 3 billion doses in 2021, that won’t be enough to cover the global population of 7 billion people. Which means that multiple companies working on the multiple vaccines is vital to finally contain the pandemic. “We can only hope that together with Pfizer and also Moderna and also Astrazeneca, we will manufacture enough doses,” Dr. Ruud Dobber, president of AstraZeneca U.S. said on CNBC’s Squawk Box Monday morning.
It’s still not clear how often people will need to be vaccinated for Covid-19
Though the results from Pfizer, Moderna and AstraZeneca all showing positive data against Covid-19 is a ray of hope in the fight against the pandemic, one open question about all of these vaccines is how long they will last against the disease. There’s reason for concern – though still rare, the number of documented cases of people being reinfected with Covid-19 is growing, which calls into question how long people remain immune to the disease, if at all. The jury’s still out on how long people might remain immune to Covid-19 naturally, with some studies finding robust immunity months later while others have found immune responses already beginning to drop off after a few weeks. All of this has implications for how long vaccine-derived immunity lasts.
The preliminary data so far suggests that Covid-19 reinfections are caused by different strains of the virus, and so further study will be needed to determine how well vaccines work in the face of multiple coronavirus strains. Flu shots are recommended to be taken every year, for example, because new seasonal strains of the flu are constantly emerging, requiring new vaccines. It may turn out that will also be the case for Covid-19, though right now it’s too early to tell.