“In clinical trials, the J&J vaccine showed 66% overall efficacy against Covid-19 while the other vaccines showed percentages around 95%. But, [Dr. Louis J. Papa, a UR Medicine primary care internist,] explains, those aren’t the numbers that matter. The question is how well the vaccines protect against serious disease.
In Johnson & Johnson’s published results, its vaccine was 85% effective in preventing severe disease and, most important, “demonstrated complete protection against COVID-19 related hospitalization and death as of Day 28.”
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Dr. Angela Branche, an infectious disease researcher at University of Rochester Medical Center who played a major role in Covid-19 vaccine trials last year, notes that the overall effectiveness percentage is a measure of “the ability of the vaccine to prevent any sort of infection that is symptomatic.”
The “ineffective” percentage could mean something as simple as a runny nose or a temporary loss of smell.
“If 30 out of 100 people who get the vaccine get a cold, does it really matter?” Dr. Branche asks. “If we have 70 percent who never get infected at all, and the remaining 30 may have asymptomatic infection or a really minor cold, then that’s an extremely successful vaccine.”