As two drug trials are halted, where does the fight against coronavirus stand?

Johnson & Johnson suspended human trials of vaccine after unexplained illness of participant

Trailers are shown in a city parking lot after a Phase 3 trial location of Johnson & Johnson's Janssen (COVID-19) vaccine candidate was announced in National City during the outbreak of the coronaviruShow more

Two more coronavirus drugs trials have been halted because of patient safety concerns. Should we believe claims that such pauses are nothing out of the ordinary, or are scientists pushing too hard in the race to produce a vaccine?

What happened?

Pharmaceutical company Johnson & Johnson announced on Monday that it had suspended human trials of its coronavirus vaccine because of the “unexplained illness” of a participant. The Phase 3 trials were set up to assess the effectiveness and safety of the vaccine in humans and were expected to involve 60,000 participants in the US and elsewhere.

The following day, Eli Lilly said it was pausing its Phase 3 trial involving the anti-viral remdesivir and another drug. The action was reportedly taken out of  “an abundance of caution” following a “potential safety concern”. As with the Johnson & Johnson trial, the precise details are unclear – as is the date when, if ever, the 10,000-participant trial will restart.

Hasn’t this happened before?

In September, trials of a coronavirus vaccine created by scientists at the University of Oxford and tested by AstraZeneca were halted after a participant developed an unexplained illness. It emerged that a healthy 37 year old woman developed transverse myelitis, causing inflammation of the spine – an extremely rare but recognised reaction to vaccination.

The huge international study restarted in mid-September, although it is still on hold in the US.

How serious are the incidents?

With no details about the precise causes, it is impossible to say. But it is likely that the incidents are demonstrations of a basic law of probability: that even extremely rare events will occur if given the opportunity.

All the trials involved tens of thousands of patients, raising the chances of at least a few rare side-effects being seen. Ironically, the fact that the trials have been halted is seen by clinical experts as proof that the testing methodology is working as it should, detecting even hints of potential problems and investigating them thoroughly before restarting the trials.

Can we trust drug companies ?

The share prices of Johnson & Johnson and Eli Lilly dipped a few per cent following the announcement, and they want the trials resumed as soon as possible. But the decision to do so is not in their hands.

Clinical trials are overseen by independent Data and Safety Monitoring Boards (DSMBs) whose decisions are made in meetings that exclude researchers and company officials. The decision to pause the Johnson & Johnson and Eli Lilly trials were made by their independent boards.

The pressure to develop a coronavirus vaccine raised concerns of researchers cutting corners. In response, Johnson & Johnson and AstraZeneca joined other vaccine makers in a pledge to apply for regulatory approval only after their vaccines passed all the standard phases of clinical trials.

Could trials be abandoned ?

Yes. The Eli Lilly trial involves a combination of drugs that has been used with few patients (although US President Trump appears to have been given the combination, alongside several other putative therapies, following his infection with coronavirus). The two components of the treatment – the anti-viral remdesivir and a so-called monoclonal antibody – are both at the cutting edge of scientific research. The Johnson & Johnson vaccine uses a modified human cold virus to trigger immunity, but it has been used for other diseases.

Even so, around one in six vaccines reaching the same stage of development fail.