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How long before we see herd immunity?

Posted at 9:22 PM, Dec 16, 2020
and last updated 2020-12-17 09:11:12-05

MAGIC VALLEY, Idaho — Although Pfizer's vaccine rolled out this week and Moderna's candidate is up for review, it won't be until 70% of the population get vaccinated before seeing herd immunity, according to one biological science professor at the University of Idaho.

With previous viruses and pathogens, only 50% of the population needed to be vaccinated to see herd immunity. With COVID-19, that number has to be higher because of how contagious the virus is.

"With this virus, it is contagious enough that we would need much higher than 50 percent. I would say between 70-90 percent of the population would need to be vaccinated to stop it from spreading," Tanya Miura, Associate Professor of Biological Sciences at the University of Idaho, said.

Her estimate is similar to Dr. Kate O'Brien's, with the World Health Organization, who said in November that 70% of the population would need to be immunized to see protection from the virus.

"So with the SARS Co-V2 virus, it's pretty infectious. It's more infectious than the influenza virus. So because of that, more people will need the vaccine to protect the population as a whole," Miura said.

Miura says the number of asymptomatic cases can cause some obstacles when it comes to building herd immunity.

"There's a chance that people who get vaccinated can get infected without showing any symptoms and still transmit the virus, and that's something we don't know from the vaccine trials yet," Miura said.

Miura also created a video to show how quickly a virus can spread depending on the percentage of people vaccinated in a population.

"You can see a real dramatic difference as you increase the vaccination or immunity rate in how the virus is able to spread through the population," Miura said.