Look at data on COVID-19 vaccines with caution, experts warn
Despite the optimism generated by the release of preliminary results from clinical trials of the COVID-19 vaccine, experts are warning much work remains to be done before a possible vaccination campaign.
“One would think that at this stage of the pandemic, we would be more suspicious and skeptical of scientific announcements made in press releases,” said Ross Upshur of the University of Toronto’s Dalla Lana School of Public Health.
“The data that has been released was preliminary data,” added Alyson Kelvin of Dalhousie University. “The trials are still ongoing.”
Two manufacturers, Pfizer and Moderna, recently announced their vaccines are 95-per-cent effective. These announcements have boosted stock markets and prompted politicians to call for rapid, widespread distribution, bringing a sense of optimism.
But we should wait a moment before rejoicing, experts say.
A 95-per-cent effective vaccine doesn’t mean it completely protects 95 per cent of recipients. It means recipients have a 95-per-cent lower chance of contracting the disease than someone who didn’t receive it.
“It’s a relative comparison,” Upshur said.
In addition, there’s still a lot of data that needs to be independently reviewed, and none of that has yet been made available. Researchers need to make sure nothing in the scientific process has distorted the results.
“It’s important to have access to the real data to see if, for example, subjects who received the placebo were at increased risk of getting the disease,” Kelvin said.
She explained Phase 3 clinical trials involve large cohorts of up to 40,000 people and normally last up to three years. The extended duration ensures no long-term adverse effects are seen.
Upshur also pointed out a 95-per-cent efficacy rate is exceptionally high. He added the results are particularly surprising given these are new technologies and new vaccines.
Both Pfizer and Moderna have filed for emergency approvals in the United States to accelerate the use of their respective vaccines.