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

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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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.

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>> 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.

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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.