Johnson & Johnson says it has temporarily paused its COVID-19 vaccine candidate clinical trials due to an unexplained illness in a study participant, delaying one of the highest-profile efforts to contain the global pandemic.

The participant’s illness is being reviewed and evaluated by an independent data and safety monitoring board as well as the company’s clinical and safety physicians, the company said.

J&J, which reports quarterly financial results on Tuesday, said that such pauses are normal in big trials, which can include tens of thousands of people. It said the “study pause” in giving doses of the vaccine candidate was different from a “regulatory hold” required by health authorities. The current case is a pause.

However, J&J’s move follows a similar one by AstraZeneca Plc. In September, AstraZeneca paused late-stage trials of its experimental coronavirus vaccine, developed with the University of Oxford, due to an unexplained illness in a UK study participant.

While trials in the UK, Brazil, South Africa and India have resumed, the US trial is still on hold pending a regulatory review.

Dr William Schaffner, a professor of infectious diseases at the Vanderbilt University School of Medicine, said by email that “everybody is on the alert because of what happened with AstraZeneca,” adding that it could take a week to gather information.

“It would have to be a serious adverse event. If it was something like prostate cancer, uncontrolled diabetes or a heart attack — they wouldn’t stop it for any of those reasons,” he said.

“This is likely to be a neurological event.”

Last month, J&J said its experimental COVID-19 vaccine produced a strong immune response against the novel coronavirus in an early-to-mid-stage clinical trial, following which the company kicked off a final 60,000-person trial, with results expected by the end of this year or early 2021.

Johnson & Johnson declined to elaborate on the illness due to privacy concerns. It did say that some participants in studies get placebos, and it was not always clear whether a person suffering a serious adverse event in a clinical trial received a placebo or the treatment.

Stat News reported the pause earlier in the day citing a document sent to outside researchers, which stated that a “pausing rule” had been met, the online system used to enrol patients in the study had been closed and the data and safety monitoring board would be convened.

Wait goes on for western nations

The team behind the AstraZeneca vaccine trial at the University of Oxford, which Australia has an early-access deal in place for, says it is working at “unprecedented speed”.

“There’s a good chance we’ll know whether the ChAdOx1 nCoV-19 vaccine is effective before the end of 2020,” the researchers said in September.

US drugmaker Pfizer Inc (with German partner BioNTech SE) and US biotech Moderna are in similar positions, with Johnson & Johnson not far behind.

Australia also has a deal in place for a vaccine being developed at the University of Queensland. That vaccine is still at phase 1 of clinical trials, with phase 3 predicted to be completed by mid-2021.

While Russia — which back in August claimed it had won the race for the world’s first approved coronavirus vaccine — and China have pushed ahead with mass public vaccination programs, the vaccines they are using have not passed final phase 3 trials.

There are concerns that Russia has prioritised national prestige over solid science and safety.

China’s emergency-use vaccination program is aimed at essential workers and others at high risk of infection, and was launched in July. That program has since seen hundreds of thousands of people vaccinated.

The wait for Australia will be longer, with the country waiting for a vaccine that passes all of the Therapeutic Goods Administration’s safety and efficacy assessments.

The United States, the European Union, the United Kingdom and the World Health Organization have also set similar minimum standards for effectiveness.

Vaccines must demonstrate at least 50 per cent efficacy — meaning there has to be at least twice as many infections among trial volunteers who got a placebo than in the vaccine group.


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