AZ pauses COVID-19 vaccine study after participant falls ill

Serious adverse event puts clinical programme on hold


AstraZeneca has put the clinical trials of its COVID-19 vaccine on hold after reporting that a participant who received the candidate experienced severe side-effects.

The phase 3 study testing the COVID-19 vaccine candidate was being undertaken at a number of sites across the US, but has now been put on hold after a suspected serious adverse reaction in a participant in the UK-based study.

AZ said in a statement that it has placed the study on hold, although the specific details of the reaction were not immediately known according to an individual familiar with the matter.

According to an AZ spokesperson, the clinical hold was “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”.

Although the details were not revealed as to the nature of the adverse reaction, the participant is expected to recover.

A phase 1/2 study of AZ’s candidate, which it is co-developing with Oxford University, demonstrated positive results against SARS-CoV-2, the virus which causes COVID-19.

The results, published in The Lancet in July, showed that the vaccine produced a robust immune response against the virus in all participants in the study.

In this early study, the vaccine appeared safe to use, although side effects were common among participants, including mild-to-moderate headache and fever.