Exposure to children associated with less severe COVID-19 among adults

Exposure to young children was associated with less severe COVID-19 illness among adults, according to a study published in the Proceedings of the National Academy of Sciences of the United States of America.

Matthew D. Solomon, MD, PhD, a cardiologist and researcher at Kaiser Permanente, and colleagues suggested that cross-immunity from exposure to endemic coronaviruses might provide some protection.

“Ever since the pandemic started, the medical community has been working feverishly to learn everything we can about the COVID-19 virus, and one of the most striking features of the virus is how it affects people so differently,” Solomon told Healio. “Some people get mild infections, while others get severe or even deadly infections. Some seem to avoid getting infected altogether.”

Endemic coronaviruses are responsible for causing nearly a third of common colds, Solomon said — a fact that prompted the investigation.

“At the beginning of the pandemic, we were all thinking about this all the time, not just scientists, but everybody was trying to figure this out,” Solomon said. “One thought that came up was, well, I wonder if people who had a lot of colds prior to the pandemic may have gotten some partial immunity from the immune response they built up to coronavirus colds.”

For an example of this, Solomon turned to his own household.

“I have kids. They're now 11 and 13, but I remember when they were much younger, and when then went to day care, we got colds all the time,” Solomon said. “That, I think, is universal for any parents of young children. One of the things that struck me about that period was, we got sick when the kids went to day care, but soon thereafter, we didn't seem to get sick anymore, even if the kid seemed to have illnesses.”

Solomon spoke to teachers and pediatricians, and found something of a “universal phenomenon,” for those in occupations where they are often exposed to young children. “Teacher friends of mine said, you had a very common and well-known idea that when you start teaching, you get sick all the time from the kids in the classroom,” Solomon said. “But eventually, you don't seem to get sick anymore. I talked to colleagues who were pediatricians, and they said that at the beginning of pediatrics residency, people get a lot of respiratory illnesses. And then it seems to go away, even though they're treating sick kids all the time. So there's this idea that you can develop some immunity that can provide some protection.”

The researchers, according to Solomon, “wanted to know what is the impact of having young children on the risk of needing to be hospitalized or needing the ICU if you got infected with COVID-19.”

Their study of active health plan members at Kaiser Permanente Northern California hospitals enrolled 3,126,427 adults, of whom 24% had children aged 18 years or younger, and 8.8% had a youngest child aged 0 to 5 years.

“Our results were striking,” Solomon said. “We were very surprised by the findings and the magnitude of the effect that we saw.”

Parents of young children experienced more SARS-CoV-2 infections — about 15% more — but adults who did not have children “were 49% more likely to be hospitalized if they had COVID-19 and 76% more likely to need the ICU, even though overall, they had a fewer number of infections,” Solomon noted.

Still, Solomon said, it is crucial that adults take the necessary protections for themselves and their children.

“Our study by no means suggests that people should not get vaccinated,” Solomon said. “The data are very clear. Vaccines have saved countless lives and are one of the greatest success stories in medical history. This pandemic has been a tragedy, and in fact, 200,000 children have lost parents to COVID-19. Our data only suggest that the potential effect we saw may provide some protection, but it’s certainly not complete protection. Vaccines and maintaining healthy behaviors are still the gold standard and critical to protect yourself against severe COVID.”