'Not going to end the pandemic': Why those hopeful vaccine trial results are not all that they seem - National Post

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“There’s lots still to be said in the background of the exciting news releases,” said Dr. Gerald Evans, head of the infectious-diseases division at Queen’s University’s medical school.

To prevent infection completely is a very high bar to achieve

It’s possible the vaccine actually prevented infection, and not just the resulting illness, but the results so far don’t show that, experts say.

“If (infections) were not lab confirmed with routine testing in all participants, then we would not know the impact on asymptomatic disease,” said Julie Bettinger, a University of British Columbia professor and vaccine-safety scientist.

Still, that may not be as worrisome as it sounds, even though asymptomatic people can spread the virus.

Actually preventing infection — as opposed to just averting symptoms or severe disease or death — is something relatively few vaccines accomplish, said Dalhousie University immunologist Dr. Scott Halperin.

A vaccine that managed merely to “downgrade” COVID-19 from a sometimes-deadly virus to a common cold would be very welcome, he said.

“To prevent infection completely is a very high bar to achieve,” said Halperin.

Evans agreed, saying a vaccine that provided “sterilizing immunity” — staving off infection itself — would be an amazing development. But even one that just afforded “protective immunity” — preventing people, especially the most vulnerable, from getting sick when they contract the virus, would be a “huge step forward,” he said.

Meanwhile, experts are debating how approval of the Pfizer and Moderna vaccines — the first to get to the finish line in a massive global effort — will affect those still to come.

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2020-11-20 15:49:06Z
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