Skip to Main Content

The study of Johnson & Johnson’s Covid-19 vaccine has been paused due to an unexplained illness in a study participant.

A document sent to outside researchers running the 60,000-patient clinical trial states that a “pausing rule” has been met, that the online system used to enroll patients in the study has been closed, and that the data and safety monitoring board — an independent committee that watches over the safety of patients in the clinical trial — would be convened. The document was obtained by STAT.


Contacted by STAT, J&J confirmed the study pause, saying it was due to “an unexplained illness in a study participant.” The company declined to provide further details. 

“We must respect this participant’s privacy. We’re also learning more about this participant’s illness, and it’s important to have all the facts before we share additional information,” the company said in a statement.

J&J emphasized that so-called adverse events — illnesses, accidents, and other bad medical outcomes — are an expected part of a clinical study, and also emphasized the difference between a study pause and a clinical hold, which is a formal regulatory action that can last much longer. The vaccine study is not currently under a clinical hold. J&J said that while it normally communicates clinical holds to the public, it does not usually inform the public of study pauses.


The data and safety monitoring board, or DSMB, convened late Monday to review the case. J&J said that in cases like this “it is not always immediately apparent” whether the participant who experienced an adverse event received a study treatment or a placebo.

Though clinical trial pauses are not uncommon — and in some cases last only a few days — they are generating outsized attention in the race to test vaccines against SARS-CoV-2, the virus that causes Covid-19.

Given the size of Johnson & Johnson’s trial, it’s not surprising that study pauses could occur, and another could happen if this one resolves, a source familiar with the study said.

“If we do a study of 60,000 people, that is a small village,” the source said. “In a small village there are a lot of medical events that happen.”

On Sept. 8, a large study of another Covid-19 vaccine being developed by AstraZeneca and Oxford University was put on hold because of a suspected adverse reaction in a patient in the United Kingdom. It’s believed that the patient had transverse myelitis, a spinal cord problem. Studies of the vaccine resumed roughly a week after it was paused in the United Kingdom, and have since been restarted in other countries as well. It remains on hold, however, in the United States. 

Johnson & Johnson began enrolling volunteers in its Phase 3 study on Sept. 23. Researchers planned to enroll 60,000 participants in the United States and other countries.

  • I’m not surprise after what we did experience in South Africa after Oxford and Witwatersrand involvement and WHO blessing. Any test which ignore Helsinki treaty of 1964 and Code of good practice recommending “laboratory tests” prior pre-clinical trial is expected to fail and its exposing human’s life. I’m filing my appeal to International Criminal Court now against the responsible of such vaccination which violates the pre-established procedures

  • I’m about sick of EVERYTHING being Trumps fault. Get over it. Things do go wrong and it’s not the fault of ONE person in America. That is such a rediculous outlook and a very narrow view point as well.

  • I expect this is a negotiating strategy by US pharma companies developing vaccines who have all halted their programs for one reason or another, after our prez did his executive order designed to drive their prescription prices down. Watch their research get back on stream as he rescinds that exec order right before the election – and watch him claim a victory.

    • If you don’t know how clinical trials work then it’s best to not make stupid political speculations out loud. If they have an adverse even, which turns out is absolutely related to the vaccine the president can’t force them to do anything. That’s the point of having multiple companies working on a compound in the same time – someone is bound to find a solution that won’t kill people. What happened to the patient in the UK is a huge deal from the clinical trial stand point.

  • “If we do a study of 60,000 people, that is a small village”
    Just a comment on semantics. I don’t think there are many “villages” in the world with 60,000 people in them outside of the NYC Metropolitan area. Maybe rarely in India and China. But generally – a village is like 50 to 5,000 individuals. 60,000 to me is a small to medium sized city.

    And I don’t think they even recruited 6,000 volunteers yet for this stage of the clinical trial/study. Hopefully just a minor unrelated illness here and with the Eli Lilly antibody treatment trials.

  • I am shocked that such a big company with “expert” scientists would not have taken detailed notes on who got the placebo and who got the actual vaccine. That seems a little suspect. My high school biology students, would have received an F if they took those kind of notes. Can’t imagine you get to that level, of research at Johnson and Johnson, and not know who received the placebo and who received the actual vaccine; that’s basic biology, control and variable, research skills.

    • @jonh: uhhh… double blind means blinded to the people receiving the med (or placebo) and blinded to the people administering it – NOT to everyone involved in overseeing the study! If that were the case, there’d be no data to evaluate when the study was over. So your dismissive response to Bex is pretty goofy and uninformed. They ought to be able to determine that easily.

    • “it is not always /immediately/ apparent”
      Everyone involved with this person needs to be blind to the condition (ie everyone recording their info). The data obviously exists, but it should not be easily accessible, and so a one day delay seems more than reasonable.

    • @RM and @Bex: That’s not how blinding works in a clinical trial these days. In a clinical trial of 60000 people, the company doesn’t maintain a ‘List’ of every patient name and the arm they are on because that’s a major privacy concern. You also can’t maintain the list at the research site as that is a potential for a blinding breach. Patients are randomized using a system (IWRS/IVRS or IXRS), where a patient is randomly assigned to one arm or another and the computer maintains that list. DSMB would not unblind a patient unless there was a specific need to blind the patient – this is so you can maintain data integrity and ensure that the patient remains evaluable. As soon as you unblind a patient, that patient becomes inevaluable after that point. The main reason you would unblind the patient is if information on which arm the patient was randomized to is important for the follow-up care to the adverse events. JNJ has thousands of scientists which includes PhDs, Medical Doctors, Epidemiologists, statisticians, computer programmers. You’re armchair quarterbacking a clinical trial with your high school diploma. Leave it to the experts on clinical trial design and development of new drugs. They’ve been doing this for over 100 years, with hundreds, if not thousands, of drugs tested on hundreds of thousands, if not millions of patients.

Comments are closed.