AstraZeneca has indicated that it may be heading for additional global trials to confirm the efficacy and clear confusion over the lower dose regimen of its potential COVID-19 vaccine that appeared to be 90 percent effective in a preliminary analysis.
AstraZeneca executives later said that high-efficacy dosage wasn’t part of the original clinical trial design but was an outcome of a dosing error.
That didn’t go down well. The two readouts, with significant divergence in efficacy, has led to an uproar among sections of the scientific community. Many experts aren't convinced about the 90 percent efficacy claim of low dose, and called it cherry-picking, and have sought more data from the company.
AstraZeneca CEO Pascal Soriot on Thursday told Bloomberg that the additional study would be to validate the dosage version that was found to have better efficacy.
Soriot said the additional study could be faster one as it requires a smaller number of participants.
Frequently Asked Questions
A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine.
There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine.
Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time.
The preliminary results of the AstraZeneca-University of Oxford vaccine were based on a total of 131 COVID-19 cases, in a study involving 11,363 participants.
The participants, who took two full doses of the vaccine, appeared to be only 62 percent effective at preventing disease, while those who got a half dose, followed by a full dose were about 90 percent effective. That latter analysis was conducted on a smaller subset of only 2,741, all from the UK.
Please read here on why AstraZeneca-Oxford potential COVID vaccine works better in low dose.
Also, a section of critics says the low efficacy in two full doses is possible due to using the same strains of adenovirus as vectors for both the prime (or first dose) and booster dose. They say that immunity to adenoviral vector from the first dose makes the second shot ineffective.
For this reason, Russian authorities have offered to try a combination of Sputnik V vaccine and AstraZeneca vaccine in additional clinical trials.
Implications on India
AstraZeneca’s 62 percent efficacy, compared to Pfizer and Moderna vaccine’s 95 percent was a bit of a dampener. India is heavily relying on the success of AstraZeneca's vaccine for a faster rollout.
To be sure, AstraZeneca’s interim analysis data exceeds the 50 percent primary efficacy endpoint set by Indian drug regulator, the Central Drugs Standard Control Organisation (CDSCO), as part of its draft regulatory guidelines for COVID-19 vaccines.
Please read here why AstraZeneca vaccines suit India
Serum Institute of India, which is developing, manufacturing and distributing AstraZeneca's COVID vaccine in India, tried to put to rest the concerns raised on the vaccine. The company said the vaccine candidate is safe and effective and the Indian trials are progressing smoothly with strict adherence to all protocols.
"Even the lowest efficacy results are at 60-70 percent, making it a viable vaccine against the virus," the company said.
AstraZeneca-University of Oxford vaccine has completed the enrolling of volunteers as part of phase-3 in India.
Influential voices like Dr Randeep Guleria, director of AIIMS, and a member of the national task force on COVID-19 management, said Serum Institute can apply for emergency use, if AstraZeneca gets UK nod for the vaccine.
Even as questions are raised about the preliminary data, the UK government seemed to be going ahead with AstraZeneca's vaccine.
Meanwhile, the UK government said on Friday it has formally asked the country’s medicines regulator MHRA to assess whether a Coronavirus vaccine developed by AstraZeneca and Oxford University should be authorised for use.
The UK government has ordered 100 million doses of the AstraZeneca vaccine, and plans to start distributing it in December, if it gets approved.
However, US nod may not be going to be easy as the vaccine would be weighed with two other COVID-19 vaccines of Moderna and Pfizer-BioNTech that have demonstrated 95 percent efficacy in early readouts.
Anthony Fauci, Director of the National Institute of Allergy and Infectious Diseases, told STAT News that he’s worried about who would get each vaccine, should the Oxford-AstraZeneca shot turn out to be less effective.“If it's 70 percent, we’ve got a dilemma” Fauci said. “Because what are you going to do with the 70 percent when you've got two that are 95 percent? Who are you going to give a vaccine like that to?" he said.