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Experts point out 'gaps' in AstraZeneca’s COVID-19 vaccine data

Experts, including those from US' FDA and CDC, have questioned the safety and highlighted the difference in the effectiveness of doses among other 'glaring absences' in the data released by AstraZeneca on November 23.

November 24, 2020 / 02:35 PM IST

Vaccine experts have noted "several glaring absences" in the data released by AstraZeneca when it claimed its vaccine candidate, being developed with Oxford University, showed an average efficacy of 70 percent, media reports have said.

Among the experts who have raised questions about the gap in information released on November 23 include those from the US Food and Drug Administration (FDA) and the US Centers for Disease Control and Prevention (CDC), CNN reported.

Spokespersons for AstraZeneca and Oxford University did not respond to questions, CNN said.

Among the questions were those included in data released by Pfizer and Moderna in their vaccine updates but were missing in AstraZeneca’s release on November 23.

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COVID-19 Vaccine

Frequently Asked Questions

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How does a vaccine work?

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.

How many types of vaccines are there?

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.

What does it take to develop a vaccine of this kind?

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.

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Here are the questions that experts want answered:

>> What data led to the conclusion of 70 percent effectiveness: While stating that its vaccine candidate showed 70 percent average effectiveness, AstraZeneca did not reveal what data led them to this conclusion.

Dr Paul Offit, a member of the FDA’s Vaccines and Related Biological Products Advisory Committee that will review all vaccines before they are put on the market, told CNN the absence of this data undermines the “significance of their findings”.

Notably, Pfizer and Moderna included this data in their results released earlier in November.

>> Specifics on participants who contracted COVID: AstraZeneca said its analysis had 23,000 participants in the third phase trial–some of whom received the vaccine candidate, some got another vaccine and the rest got saline placebos. An independent board then analysed the extent to which the group that received the vaccine candidate was protected.

The release said 131 participants developed COVID-19 but failed to say in which group (candidate vaccine, placebo, etc) of participants they belonged.

Check here for the latest updates on all COVID-19 vaccines

>> Questions on safety: The AstraZeneca trial was put on hold twice by the UK government due to concerns over the health of two participants before being allowed to resume. But, AstraZeneca’s statement says there was “no serious safety events related to the vaccine” and that it was “well tolerated”.

“I want to know specifics about the serious adverse reactions which caused the trials to pause,” said Dr William Schaffner, a member of the CDC’s Advisory Committee on Immunization Practices that will also review all vaccines before they are put on the market.

>> Difference in effectiveness between doses: The study had two different dose regimens—one had 2,741 participants who received a half-dose and then a full dose at least a month later; while the second batch of 8,895 participants received one full dose followed by another full dose at least a month later.

The first batch had 90 percent efficacy, while the second batch saw 62 percent protection. Dr Adrian Hill, one of the lead Oxford researchers, said determining the reason could take “weeks and months” as they “don’t fully understand, but there’s several ideas” which are being explored.

Also Read: SII can apply for emergency use authorisation in India if AstraZeneca gets UK nod

AstraZeneca’s vaccine trials in other countries are still underway. Together these bring the total number of participants to 60,000 by 2020-end.

One reason, according to Yale School of Medicine vaccine specialist Dr Saad Omer, could be that the first group had fewer participants, which means a larger pool might not yield similar results.

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Moneycontrol News
first published: Nov 24, 2020 12:51 pm

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