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Here is what we know about drugs and vaccines: If tested in rigorous clinical trials and shown to be safe and effective, they make the world a healthier place.

Here is another thing we know about drugs and vaccines: They are not easy to develop.

The latest reminder came Tuesday, when Eli Lilly paused an ongoing study of its experimental treatment for Covid-19. Less than 24 hours before, Johnson & Johnson paused its own massive SARS-CoV-2 vaccine trial. In each case, the companies followed the advice of a data and safety monitoring board, or DSMB, the all-important, seldom-discussed experts who keep tabs on every well-run trial.


To clinical trial experts, these pauses are heartening, a sign that the scientists in charge are prioritizing the safety of volunteers and future patients — that the system is working. But in the midst of a furious race to develop Covid-19 vaccines and therapeutics, outsiders can’t help but wonder: Are these pauses a reason for serious concern? 

The answer, at least for now, is that it’s impossible to know. 


Take the Johnson & Johnson announcement of a pause, made after an unexplained illness in a study participant. Is it possible that the participant received the vaccine and became ill because of it? Yes. In that case, there’s a real possibility that J&J could place a clinical hold on its trial, or have one placed on it by the Food and Drug Administration. Just last month, AstraZeneca placed a clinical hold on its Covid-19 vaccine trial — one that still has not been lifted in the United States, though it has been in other countries.

Two clinical holds placed on two of the frontrunners in the so-called vaccine race would be a testament to how challenging the road ahead could be, and perhaps even a worrying sign more broadly about the development of Covid-19 vaccines.

But it’s important to remember that the J&J news could amount to … a blip. The participant who became ill might have been in the control group of the trial and received a placebo. Or, perhaps the participant was in the vaccine group but researchers determine that the illness, whatever it was, was not caused by the vaccine. In this scenario, there might not be a full clinical hold, the pause can be lifted, and the trial will resume enrollment.

So, too, with the pause in Eli Lilly’s trial, which compares the company’s investigational antibody treatment against Gilead Sciences’ remdesivir. At this point, Lilly doesn’t know what the issue is, and it doesn’t know whether the DSMB’s concern is related to a patient who received the antibody alongside remdesivir or just remdesivir alone. And, perhaps most important, the company has no idea how long it’ll be before the independent experts say the trial can safely resume.

It’s either a sign of trouble, or a bump on the way to success. 

Drugs and vaccines are a marvel of modern science. But it’s easy to forget that behind every marvel there is hard work — and risk.

  • These are great examples of why no one from the media, physicians, political leaders, or anyone else who thinks they were knowledgeable should have been hyping that “we’ll have a vaccine by…” It DOES take time to do this safely.

  • It seems clear that with all these bumps, America First sadly would not happen now. I wonder whether it would be feasible and acceptable for US Citizens to travel to UK to get vaccinated for either the Astra-Zeneca or the Moderna vaccine since it seems more likely that they would be approved there before in the US.

  • Info on the one sick patient likely has become un-blinded, and if that person was in the placebo group then the trial would have resumed. As the trial remains on hold in a scenario where time is of the essence, it can be safely assumed that the patient reacted to the drug / vaccine being tested. That warrants thorough investigation, and that takes time that is well worth the safety of future millions of vaccine recipients.

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