Since the COVID-19 vaccines were approved for emergency use by the FDA, pediatricians at Eugene Pediatric Associates have been fielding questions daily from families wanting to know more about them and what it will take to achieve herd immunity.

“We believe, based on current science – which is of course always changing – that about 70% of our population will need to be immune to SARS-CoV2, coronavirus, in order for us to have adequate herd immunity,” says Dr. Pilar Bradshaw.

What is herd immunity?
Herd immunity is achieved when enough people are immune to a viral disease that it can no longer spread easily among a community or “herd.” A large population that is immune will naturally help protect people in the community who are at risk.

For example: If you have a group of 100 people and 99 are immunized against an illness, the one person in the middle of the “herd” who decided not to vaccinate is probably safe, because the germ is likely not going to be able to get a foothold in that group.

“If you compare that to a herd where 20 people out of 100 decide to immunize, then the other 80 are at risk. That’s where the virus is going to attack,” Dr. Bradshaw says.

The more contagious a disease is—like COVID-19—the greater the proportion of the population that needs to be immune to the disease to stop its spread. Measles, for example, is highly contagious, requiring around 95% of the population to be vaccinated before herd immunity is reached.

“The only way to accomplish that is either by having many, many more infections and deaths, which is not desirable, or to vaccinate with the COVID-19 vaccine,” she says.

Reaching the levels of infection needed to achieve herd immunity without a vaccine could be devastating and potentially overwhelm health care systems, leading to an extraordinary number of deaths. A vaccine is a much safer way to build immunity against the virus, says Dr. Bradshaw.

What if I’ve had COVID-19? Do I still need to be vaccinated?
The answer is yes.

“We don’t know if getting coronavirus gives you immunity for a very long time,” she says. “At this point, we only really know you have immunity for about three months, then you could get it again. We have much more confidence in the ability of the vaccine to give you a set amount of immunity. We also have studies that are well-designed that are showing us how effective that vaccine is, and those studies are ongoing.”

It’s possible that vaccine boosters could be necessary, similar to how a flu shot is recommended every year.

To reach 70% herd immunity for COVID-19, medical providers agree that it will require more people who are willing to get vaccinated when the vaccine becomes available to them.

“Because if we cannot get to 70%, our most fragile community members will still be at risk of getting sick and dying from this very serious virus,” Dr. Bradshaw says.

In addition to people’s willingness to be vaccinated, achieving herd immunity will depend on the vaccine supply, which has been slow to roll out to states, including Oregon.