CHICAGO – More than 500 Illinois residents, most of whom are older and have underlying health conditions, have been hospitalized because of COVID-19 despite being fully vaccinated, according to data from the state health department.
But experts say the chances of getting a so-called breakthrough infection remain very low. In all, about 5.9 million Illinois residents are fully vaccinated.
“Right now, they are still very rare,” Dr. Ramon Lorenzo-Redondo, a COVID-19 scientist and researcher at Northwestern University Feinberg School of Medicine, said of breakthrough infections. Even with the new delta variants, the protection rate offered by vaccines continues to be high, he said.
Of the 518 people who had been hospitalized as of Wednesday, 33% had diabetes, 22% had chronic kidney disease, 22% had immunocompromised conditions, 4% had autoimmune diseases and 3% had chronic liver disease, according data that had not been released by the state health department before this week.
The bulk of the patients — 83% — were age 60 and older. Just over 70% of the patients were white and 17% were Black.
As of Wednesday, 141 people in Illinois had died because of breakthrough infections, according to the state, representing about 2% of all COVID-19 deaths in Illinois since the start of this year.
It’s possible that many more than 518 people have gotten breakthrough infections in Illinois, but the state doesn’t report breakthrough infections that don’t involve a hospital stay or lead to death. Some people with breakthrough infections also may not know they had them because they were asymptomatic or didn’t get tested, Redondo said.
“You’re not getting the full data,” Redondo said. “You are just getting a portion.”
Still, based on what’s known, he and other experts say breakthrough infections are uncommon.
“The risk is still exceedingly low for breakthrough infections,” said Dr. Stephen Schrantz, a co-investigator in clinical trials of the Moderna and Johnson & Johnson vaccines at University of Chicago Medicine.
A study published in the New England Journal of Medicine last month found that of 417 people who received Moderna or Pfizer vaccines and were regularly tested after being fully vaccinated, only two — or less than half a percent — caught COVID-19.
Also, the Centers for Disease Control and Prevention received reports of 10,262 breakthrough infections through April 30. As of that date, about 101 million people in the U.S. had been fully vaccinated.
The CDC report about those infections noted that it’s likely many more people got breakthrough infections than were reported. The CDC has since changed its reporting, now only tracking breakthrough cases that result in hospitalizations and deaths.
Experts have long cautioned that no vaccine is 100% effective. The Moderna and Pfizer vaccines were found to be 94% and 95% effective, respectively, in preventing COVID-19 during clinical trials, and the Johnson & Johnson vaccine was found to be 66% effective. All three were found to be highly effective at preventing severe cases of the illness.
“This is not a barrier so the virus never infects you again,” Redondo said of vaccines. “You are well-protected, but some people are still going to be infected.”
Some people, such as those with compromised immune systems because of organ transplants, or autoimmune disorders such as lupus or rheumatoid arthritis, might not develop a strong enough immune response to a vaccine to keep them from catching COVID-19.
It’s also possible that variants could lead to more breakthrough infections, though so far the vaccines seem generally effective against them, according to studies.
In recent weeks, Americans have become increasingly concerned about the delta variant, which seems more contagious than other variants. The delta variant is now the dominant variant in the U.S., though there were only 208 known cases in Illinois as of Wednesday.
A study out of Britain found the Pfizer vaccine to be about 88% effective against the delta variant, though data out of Israel, where the delta variant is dominant, showed the Pfizer vaccine to be 64% effective against all coronavirus infections.
Moderna and Johnson & Johnson have both said their vaccines are effective against the delta variant.
“I think with time we’ll have a better understanding of how the delta variant and vaccine and breakthroughs work together,” Schrantz said. “But for now what we can tell is the vaccines still hold up pretty well against the delta variant, particularly in (preventing) severe illness.”