PARIS – None of the trials of COVID-19 candidate vaccines can detect a reduction in serious outcomes such as hospitalization or death, a leading public health expert said Thursday.
Writing in the BMJ medical journal, associate editor Peter Doshi warned that not even phase 3 trials under way in the race for a vaccine can prove their product will prevent people contracting COVID-19.
In a sobering essay, Doshi said those hoping for a breakthrough to end the pandemic would be disappointed, with some vaccines likely to reduce the risk of COVID-19 infection by only 30 percent.
“None of the trials currently under way are designed to detect a reduction in any serious outcome such as hospital admissions, use of intensive care, or deaths,” he wrote.
“Nor are the vaccines being studied to determine whether they can interrupt transmis – sion of the virus.”
The World Health Organization (WHO) has identified 42 candidate vaccines in clinical trials, ten of which are in the most advanced “phase 3” stage.
This is where a vaccine’s effectiveness is tested on a large scale, generally tens of thousands of people across several continents.
But Doshi, assistant professor of pharmaceutical health services research at the University of Maryland School of Pharmacy, said that even the most advanced trials are evaluating mild rather than severe disease.
This may be down to the numbers of people involved in trials, he said, pointing out that the majority of confirmed COVID-19 infections involve mild or no symptoms.
And few if any current trials are designed to find out whether there is a benefit among the elderly, a key atrisk constituency.
Without enrolling frail and elderly volunteers in trials in sufficient numbers, Doshi said there can be little basis for assuming any benefit against hospitalization or mortality.
He added that children, immunocompromised people and pregnant women had largely been excluded from trials, making it unlikely that the experiments will address key gaps in our understanding of how COVID-19 develops differ – ently among individuals.
Vaccine test volunteer dies
Several trials have already been halted after participants became ill.
In Brazil, a volunteer participating in clinical trials of the COVID-19 vaccine developed by Oxford University has died, officials announced Wednesday, though media reports said he had received a placebo, not the test vaccine.
It is the first death reported in the various coronavirus vaccine trials taking place worldwide.
However, organizers of the study said an independent review had concluded there were no safety concerns and that testing of the vaccine, developed with pharmaceutical firm AstraZeneca, would continue.
Media reports said the volunteer was a 28-year-old doctor working on the front lines of the pandemic who died of complications from COVID-19.
Brazilian newspaper Globo and international news agency Bloomberg said he was in the control group and had received a placebo rather than the test vaccine, citing sources close to the trials.
“Following careful assessment of this case in Brazil, there have been no concerns about safety of the clinical trial, and the independent review in addition to the Brazilian regulator have recommended that the trial should continue,” Oxford said in a statement.
AstraZeneca said medical confidentiality meant it could not give details on any individual volunteer, but that independent review had “not led to any concerns about continuation of the ongoing study.”
30% risk reduction
Many countries plan to prioritize vulnerable people once a vaccine is available, but Doshi said that those hoping for a miracle end to the pandemic would have to wait. He said that several pharmaceutical firms had designed their studies “to detect a relative risk reduction of at least 30 percent in participants developing laboratory confirmed COVID-19.”
Recent studies have also confirmed that it is possible for someone to be reinfected with COVID-19, a development that may impact how governments’ form their vaccination.