COVID-19: Top science stories of the week, from paused vaccine trial to immune profile of infected children

Vaccine trial on hold due to possible adverse reaction

Phase III clinical trials for the coronavirus vaccine developed by AstraZeneca and Oxford University, have been paused after a participant involved in the trial had a suspected adverse reaction.

The New York Times reports that a volunteer in the UK trial has been diagnosed with transverse myelitis, an inflammatory syndrome that affects the spinal cord and can be caused by viral infections. However, the cause of the illness has not been confirmed and an independent investigation will now work out if the reaction was linked to the vaccine or not.

Following successful Phase I and II clinical trials earlier this year, the AZ-Oxford vaccine moved into final stage (Phase III) testing in recent weeks, involving some 30,000 participants in the US, UK, Brazil and South Africa.

There are currently nine vaccine candidates in Phase III trials. The AZ-Oxford vaccine is considered a front-runner, with late-stage clinical trials under way around the world, with hopes to have a vaccine ready before the end of the year.

The vaccine uses an adenovirus that carries a gene for one of the proteins in SARS-CoV-2, the virus that causes Covid-19. The adenovirus is designed to trigger the immune system to generate a protective response against SARS-2.

In a statement, AstraZeneca described the trial’s halt, as a “routine action which has to happen whenever there is a potentially unexplained illness in one of the trials, while it is investigated, ensuring we maintain the integrity of the trials.”

The company said it was “working to expedite the review of the single event to minimize any potential impact on the trial timeline,” and reaffirmed its commitment “to the safety of our participants and the highest standards of conduct in our trials.”

Children with severe COVID-19 reaction show unique immune profile

Although COVID-19 is mild in most children, several hundred children worldwide have reportedly developed severe hyperinflammatory disorders one to two months after infection that have led to multiple organ failure, and even death in some cases.

Scientists at the Karolinska Institute in Stockholm are now trying to figure out the biology of this rare and devastating condition, called multisystem inflammatory syndrome in children (MIS-C).

To understand MIS-C’s biological profile, they looked at 13 children with MIS-C, 28 children with Kawasaki’s disease (which shares overlapping features with MIS-C) and 41 with mild COVID-19. The researchers reported that compared with children with Kawasaki’s disease, those with MIS-C have lower levels of an immune chemical called IL-17A, which has been implicated in inflammation and autoimmune disorders.

Unlike all the other children studied, children with MIS-C had no antibodies to two coronaviruses that cause the common cold. It is possible that this deficit might be implicated in the origins of their condition.

More research is needed, with a larger number of children, to further understand the reasons why some children have mild COVID-19, and others go on to develop MIS-C.