NIAID statement on the DSMB expressing concern about information released by AstraZeneca on initial data from its COVID-19 vaccine clinical trial in the US


The National Institute of Allergy and Infectious Diseases (NIAID) has released a statement that the Data and Safety Monitoring Board (DSMB) has expressed concern that AstraZeneca may have included outdated information from the US clinical trial of their COVID-19 vaccine, and that this information may have provided an incomplete view of the efficacy data.

This article was published on
March 23, 2021

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What our experts say

Context and background


Media briefing

Media Release

Expert Comments: 

Prof Stephen Evans

It is not unknown for a DSMB todisagree with investigators over interpretation of trial results.

It is usually done in private, sothis is unprecedented in my opinion.

I have said frequently that‘headline’ estimates of efficacy being compared between trials is veryunreliable.

The DSMB has responsibilityessentially for safety of participants, not efficacy unless it is either sohigh or so low or negative that it is unethical to continue to randomise, so insome senses they might be seen to be exceeding their brief. If the protocol foran interim analysis gave a cut-off at a given number of events accrued, then AZmight be justified in sticking to that. However if AZ had not adhered to theprotocol then obviously the DSMB are justified in raising the issue.

One explanation might well bethat this trial is currently being conducted when there is a large amount of anew variant about more recently, and, as might be expected, the efficacyagainst that variant might be less, so more recent data shows reduced efficacy.Of course the other vaccines may also show such reduced efficacy and we don’tknow by how much.

It does not leave me concernedparticularly unless they had found a safety issue that was being hidden, whichdoes not appear to be the case.

Dr Stephen Griffin

For me, this further announcement by the DSMB in response to the AZ release yesterday highlights the importance of data being provided at the same time as summaries being made public. Naturally, the news yesterday was taken in good faith and the issues raised by the DSMB may be a mere technicality, yet this won’t be clear until we have full disclosure. Nevertheless, we must ensure that issues such as this are dealt with appropriately and that idle speculation is not seized upon by groups seeking to undermine faith in vaccination programmes.

Dr Peter English

There is a single sentence behind this story:

The DSMB expressed concern that AstraZeneca may have included outdated information from that trial, which may have provided an incomplete view of the efficacy data.’

I find this problematic in various ways. It reads like a sentence from the conclusions of a paper; but one that has been presented out of context, without any explanation of the reasons for drawing the conclusion, or of what they think the consequences might be.

If you present data, stating the period in which the data were collected, how can the data be ‘outdated’. The AstraZeneca press release did say it was on ‘interim’ data. There may be more recent data; but that would not normally ‘outdate’ or invalidate the interim results. 

Note also the use of the subjunctive ‘may’, used twice in that sentence.

In my opinion this is shamefully bad communication by NIH as with their lack of clarity they have left room for speculation which could be damaging for vaccine uptake.

If asked to speculate about what underlies this, I would guess that they may be making the same points that I made in my earlier rapid response: 

One thing that is not clear in this press release is whether the study provided any information on the real-world efficacy of the vaccine against different variants of the virus.  There is no information on whether genomic typing of the cases was undertaken, the prevalence of different variants in the study population, or the dates during which the data were collected (which would allow some inferences to be drawn on variant prevalence and thus vaccine efficacy against the variants).  We know from other work that the vaccine seems to be highly effective against many variants, in particular, the more transmissible B.1.1.7 variant; but we do not know if the study will add to our knowledge on this.


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