A pause in the late stage trial of a Covid-19 vaccine shows that proper processes are being followed and that it is not a "rush job", clinical virologist Dr Chris Smith says.
A scientist at the Oxford Vaccine Group's laboratory facility at the Churchill Hospital in Oxford, west of London in June. Photo: AFP
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The Oxford University AstraZeneca trial was paused earlier this week after a person who received the vaccine in the UK was hospitalised with neurological complications.
The Oxford vaccine is now in phase three trials, which means big trials on large groups of people.
There is also a control group of other people who have had a vaccine but they do not know which one - the control group has in fact had a meningitis vaccine, Dr Smith said.
He said the trial was going well, but unfortunately a few days ago the news came out that it had been halted because one of the recipients developed a case of transverse myelitis, which is an inflammatory condition of the spinal cord which causes sensory and motor deficits.
"So we only know that there is a case of transverse myelitis and for cautionary reasons the trial has been temporarily suspended while this is investigated."
But Dr Smith said the condition is not only linked to vaccination and it can also happen by chance to some people.
"So it may well be that a person who has had this vaccine was going to get transverse myelitis anyway and the two are not connected.
"On the other hand they might be because vaccines provoke an immune response and in some people there may well be onward domino effects within the immune system and this can culminate in off target effects and that's why it needs investigating."
Dr Smith said because the vaccine is potentially going to be administered to millions of people.
"So it's very important to understand what the side effect profile is and therefore reassure yourselves that actually this was a one off, it was nothing to do with the vaccine or if it is something to do with the vaccine, try to understand why that's happened."
He said the trial is paused in order not to expose anyone to an unsafe situation.
"But this [a trial being paused] is not the first time it's happened, it happens quite frequently and we shouldn't be too perturbed, in fact we should be reassured because if these sorts of things are being picked up and monitored, it actually shows us that the proper channels, the proper processes are being followed - this is not a rush job."
Dr Smith said there are a number of factors which may help determine whether the transverse myelitis was caused by the vaccine.
For example, whether the person was in the control group, whether this person has any history of getting auto immune conditions and when the vaccine was administered in terms of when the transverse myelitis occurred.