Why we aren’t seeing a surge in severe COVID-19 infections?

CDC surveillance data now show that over 85% of all COVID-19 infections in the United States appear to be due to the BA.2 virus variant, with Omicron BA.1 making up the rest. 

While there are some increases in U.S. infections in pockets of the country, there certainly has not been a major increase in infections, and hospitalizations remain low. This contrasts with the documented increases seen with BA.2 in England and Israel.

New, confirmed COVID-19 infections in the US, UK and Israel. Note the

Some public health figures have argued that we are not seeing an increase in infections because of “poor reporting” of COVID-19 infections in the U.S. They point to reports circulating of increases in wastewater COVID-19 levels, and anecdotal accounts of many people having mild infections. 

New US cases, hospitalizations and deaths. The omicron surge, while much lower per capita than in Israel, was still very significant in the overall number of infections. Note that there is no apparent increase in infections at this time, and the number of tests remains consistent. From the NYT.

Others point out that now, with home testing and treatments, infected individuals are not being counted because they’re simply self-isolating after a positive test rather than contacting their doctor or going to a screening center for confirmation. This actually sounds like a good idea to me because it prevents transmission, and these days you can’t even get an appointment with a physician! A few authorities simply think that hospitalization increases are coming soon.

In any case, I believe that there may be another cause for the lack of hospitalizations and serious illness despite the potential of more circulating virus.

While it has been reported that the U.S. is still only 77% COVID vaccinated, that number includes children under the age of 5 years who are not vaccine eligible. In fact, the CDC now reports that at least 82% of individuals approved for COVID-19 vaccine in the U.S. (>5 years old) have received at least one dose of the vaccine. Importantly, given current usage almost all those doses are now the more effective mRNA vaccines from Moderna and Pfizer. 

In at risk populations over the age of 65, 95% of people have received at least one dose of these vaccines and 90% are fully vaccinated. While only 2/3 of these over 65 individuals have had boosters, this overall vaccination rate in the most susceptible to serious illness and death is incredibly encouraging and suggests a high degree of background immunity in the U.S. And vaccination has clearly contributed to the decreases in hospitalization.

Hospitalization rates in vaccinated vs. unvaccinated populations over the past year (top) and past 6 months. From the CDC.

However, there has been another source of immunity that has been overlooked. According to CDC seroprevalence data we are approaching 50% of the U.S. population having been infected with COVID-19! While there is some debate about the degree of immunity from this, most infected people have some protection after infection.

The combination of vaccination and infection (breakthrough) gives antibody immunity as good or better that a booster shot.

More importantly, the combination of immunity from even a single dose of the vaccine and infection appears to be very potent. A recent unreviewed publication shows what many have anticipated — that the combination of infection and vaccination potently increases immune protection.

The combination of slow but ever-increasing immunity from both vaccines and infection suggests that we are finally approaching levels of herd immunity. This suggest that we have reached a place where new infections from COVID-19 variants will not cause the pandemic surges of serious illness that we’ve previously observed. Let’s hope this is the case.

Published by jbakerjrblog

Immunologist, former Army MD, former head of allergy and clinical immunology at University of Michigan, vaccine developer and opinionated guy.

One thought on “Why we aren’t seeing a surge in severe COVID-19 infections?

  1. Anecdotally, son away at college (MI) visited at Easter. Told us he tested before joining us at church and was negative. I asked if he felt sick/why did he test-he said because most of the frats/sororities are getting hit hard with illnesses & positive tests.
    His frat was hit hard back in Nov with Delta swooping through. He said none of his frat brothers were sick this time around.
    This college has mandated 2 vaccines. Some have 3. He said he’s fairly sure the sick students were not reporting their illnesses/positive status.


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