AstraZeneca’s logo is reflected in a drop on a syringe needle. Photo: Reuters/Dado Ruvic/Illustration/File Photo.
AstraZeneca said on Monday its vaccine candidate for the novel coronavirus, developed along with the University of Oxford, showed an ‘average’ efficacy of 70% in protecting against the virus in two study segments.
AstraZeneca has become the latest drugmaker to unveil positive interim data in a race to curb the COVID-19 pandemic. The data was obtained from late-stage trials in Britain and Brazil. According to AstraZeneca, it indicates that the vaccine candidate was 90% effective in preventing COVID-19 when administered as a half dose followed by a full dose at least one month apart.
Another dosing regimen showed 62% efficacy when given as two full doses at least one month apart and the combined analysis from both dosing regimens resulted in an average efficacy of 70%. All results were reportedly statistically significant.
No serious safety events related to the vaccine have been confirmed and it was well tolerated across both dosing regimens, the company added.
The company also added that the efficacy could be ‘improved’ to 90% without any serious side-effects in the currently lower-efficacy regimen – presumably with an eye on results previously announced by Pfizer and Moderna for their vaccine candidates, both reportedly higher than 90%.
“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,” Pascal Soriot, Astra’s chief executive, said in a statement.
The British drugmaker’s preliminary trial results mark a fresh breakthrough in the fight against a pandemic that has killed nearly 1.4 million people and roiled the global economy.
The interim analysis was based on 131 infections among participants who received the vaccine and those in a control group who were given an established menengitis shot.
The data comes after US rivals published interim data in recent weeks showing efficacy of more than 90%. On November 16, US-based Moderna Inc said its experimental vaccine proved to be 94.5% effective based on an early data analysis.
A week earlier, Pfizer Inc and Germany’s BioNTech SE said their vaccine candidate had demonstrated greater than 90% efficacy, rising to 95% with analysis of full-trial data.
Russia’s Sputnik-V vaccine on November 11 was also shown to be more than 90% effective, but it was based only on 20 infections, thus rendering the results unreliable.
However, the safety of these vaccines and the conditions of their administration aren’t yet clear. Researchers have previously said these details could become clear only after the vaccine candidates’ phase 3 clinical trials are complete.
As Sandhya Srinivasan wrote for The Wire Science on November 15:
First, the clinical trials to test the COVID-19 vaccine candidates are designed such that any vaccine that is proven to be effective will have limited value. …
Peter Doshi, an assistant professor of pharmaceutical health services at the University of Maryland and associate editor at the BBMJ, has argued that the phase-3 COVID-19 vaccine trials are not designed to test for what we need to know – whether the vaccine candidate will prevent severe disease. He pointed out that the primary outcome for these vaccine trials is simply a laboratory-confirmed case of infection with SARS-CoV2, with at least one symptom – which could be as mild as a cough, fever or diarrhoea.
In Prof Doshi’s testimony to a US Food and Drug Administration (FDA) committee on the COVID-19 vaccine, he said that the vaccine candidates should be tested for how well they prevent severe illness leading to hospitalisation, ICU stay or death. The trials either don’t measure this or they are not set up to measure it well. In fact, the researchers stop the trials when they meet their target of 150-160 cases.
In order to evaluate efficacy against severe disease, these cases need to include sufficient numbers of severe disease, which is unlikely to happen, as severe disease is much less common than mild forms of the disease. The trials are also not designed to measure whether they reduce illness in those at greater risk, such as the elderly, or those with comorbidities. And they don’t collect the information needed to know if the vaccine could reduce transmission of the disease to bring the pandemic under control.
Over the weekend, Bharat Biotech in India had reported preliminary results from trials of its vaccine candidate as well – Covaxin – announcing an efficacy of 60%.
Both Pfizer’s and Moderna’s vaccine candidates employ the more advanced mRNA vaccine technology. The AstraZeneca vaccine uses a modified version of a chimpanzee common cold virus to deliver instructions to cells to fight the target virus, which is different from the mRNA method.
Bharat Biotech’s vaccine candidate’s precise design is unknown. However, the company has previously invested in and collaborated with the Jefferson Vaccine Centre (JVC), Pennsylvania – and JVC announced a vaccine candidate in April this year that it called Coravax. Coravax uses an inactivated rabies vaccine to carry the novel coronavirus’s spike protein into the body.
But Prizer’s and Moderna’s vaccine candidates seem to be infeasible for India’s use (as explained here), whereas both Bharat Biotech’s and AstraZeneca’s candidates could have greater local demand.
(With Reuters inputs)