Ask A Doctor: How Promising Are The COVID-19 Vaccines, And How Many People Need To Get One?

A UT Health San Antonio physician answers listeners’ questions about their health during the coronavirus pandemic.

By Michael Marks & Caroline CovingtonDecember 7, 2020 11:49 am,

In this installment of Ask a Doctor, UT Health San Antonio physician Dr. Fred Campbell answers more of Texas Standard listeners’ most pressing questions about the coronavirus.

Why do flu vaccines appear to be so much less effective than the COVID-19 vaccines?

The influenza virus often mutates, so it’s difficult for vaccine developers to predict how effective a vaccine all be.

“That seems to be the the M.O. of the influenza vaccine. And then some individuals that are real high risk, particularly the very elderly, may not mount the immune response to influenza vaccine that they appear to be mounting to the COVID-19 vaccines,” Campbell said.

What percentage at the population needs to be vaccinated in order to create widespread immunity to COVID-19?

So-called herd immunity happens when the rate of new infections drops dramatically.

“It can be anything from 50% to almost 100%. So, there’s a wide range and it depends on several factors,” he said.

Those factors include how contagious the disease is, how effective the vaccine is and whether the coronavirus mutates.

Campbell estimates that for herd immunity to take effect with COVID-19, about two-thirds of Americans will either need to be vaccinated or have been exposed to the virus.

How promising are the Pfizer-BioNTech and Moderna vaccines for stopping the pandemic?

So far these vaccines appear to be highly effective, with limited risk. There’s always the possibility that could change as the vaccine is doled out, Campbell says. Still, he advocates strongly for getting vaccinated.

“I’m a big proponent of vaccination. And with this particular set of vaccines, I think we have the chance of, again, reaching that herd immunity point relatively quickly, much [more] so than we had anticipated,” he said.

If you found the reporting above valuable, please consider making a donation to support it here. Your gift helps pay for everything you find on and Thanks for donating today.