How many Americans have had covid

April 26, 2022

How Many?

A new CDC study attempts to tackle the looming question: How many Americans have had prior infection from the virus that causes COVID-19 (whether or not they knew it)?
What we're learning and why it matters.

The Study

  • The CDC study spans from September 2021 to February 2022 — when “national COVID-19 case rates peaked at their highest recorded levels.”
  • The CDC regularly scanned blood samples for a specific antibody produced by the virus that causes COVID-19 (not by the vaccine) to estimate prior infection.
  • Results: The percentage of Americans with evidence of prior infection jumped from roughly 33% to more than 57% during the spread of Omicron; the prevalence amongst children was even higher — more than 75%.

Why Does This Matter?

  • Having a better idea of how many people have had prior infection will help us better understand immunity concerning the new coronavirus — how our bodies react to it, transmit it and protect against it.
  • This new research suggests more than half of all Americans — and 3 out of 4 children — have had a prior COVID-19 infection.
  • The study’s leader says the higher rates of evidence of prior infection in those 17 and younger may be due in part to the lower rates of vaccinations in this group.
“We still do not know how long infection-induced immunity will last …"

Dr. Kristie Clarke, who led the study and concedes recent infection means “you may be able to wait [longer] on your second booster dose” — but the CDC study also states that prior infection “should not be interpreted as protection from future infection. Vaccination remains the safest strategy for preventing complications from SARS-CoV-2 infection …”

"Giving an annual shot without running a randomized control trial showing improvement in severe disease and hospitalization and even death would be foolish."

Dr. Vinay Prasad, MD, MPH. Separately, on the same day the CDC released this new study, Pfizer applied for emergency use authorization for a booster dose for its COVID-19 vaccine for children 5-11. Dr. Prasad was responding to an article from STAT News entitled “Experts fear U.S. may default to annual Covid boosters without sufficient data” (we’ve linked to this article on our source page).

One limitation of the study? The CDC says it may *underestimate* the overall number of infections — since those infected after vaccination may have lower levels of the specific antibodies looked for (b/c their bodies are “primed” to fight off infection), AND because the test can’t show how many times a person has been infected.

We’ve covered the ongoing debate of prior infection (aka “natural immunity”) vs. vaccine induced-immunity, & we’ve heard from doctors w/ differing points of view — from the importance of vaccines, to the power of natural immunity, or a combo of both. This is still a developing story which we’ll continue to cover!

Link to pdf of the study

CDC estimates 3 in 4 kids have had coronavirus infections (Associated Press)

Nearly 60% of Americans now have antibodies from Covid-19 infection, CDC study finds (CNN)

Dr. Vinay Prasad, MD MPH, response to the STAT News article

Experts fear U.S. may default to annual Covid boosters without sufficient data (STAT News)

by Jenna Lee,