Post-Covid-19, World Risks Having to Pay Off ‘Immunity Debt’

Many people had little exposure to common viruses during social distancing, meaning bugs could spread more quickly once countries reopen

By Miho Inada of The WSJ. Excerpts:

"Doctors in France are calling it the immunity debt: When people avoided each other during the pandemic, they failed to build up the immunity against viruses that comes from normal contact.

As regular life resumes, society may find payments on that debt coming due, in the form of worse-than-normal viral disease outbreaks.

In early June, 16-month-old Toranosuke Tsukidate came down with a common virus that caused a fever topping 106 degrees Fahrenheit. The bug was spreading rapidly through his Tokyo daycare, said his mother, Miwako Tsukidate, 27, and the boy was hospitalized for oxygen treatment for a week.

By the time Toranosuke was discharged, his mother observed the beds around him filling up with children suffering the same ailment, which is usually more common in the fall. “I was surprised to see how it took off so quickly, and I was also surprised to see it spreading at this time of the year,” Ms. Tsukidate said.

At Perth Children’s Hospital in Australia, infectious diseases researcher David Foley isn’t surprised. His country experienced a similar out-of-season flare-up of the virus that infected Toranosuke—respiratory syncytial virus or RS virus—during the Southern Hemisphere’s summer months following an unusually quiet winter.

There was “an increased population that was susceptible, helping the virus to spread more easily,” Dr. Foley said. “Similar to starting a fire, the more kindling present, the easier it is for a spark to take hold and burn brightly.”"

"As people strove to avoid the virus that causes Covid-19, they ended up staying away from many other viruses and bacteria that cause common ailments—influenza, chickenpox, strep throat, RS virus and more. Now as normal life resumes in many countries, exposure to those bugs is returning, too."

"At Maimonides Children’s Hospital in Brooklyn, N.Y., Rabia Agha, director of the pediatric infectious diseases division, encountered an RS virus wave this spring. She found the median age of infants treated was just 6 months, down from 17 months the previous season. The immune system of small babies tends to be weaker, so more of this year’s patients ended up in intensive care."

"In the U.S., the Centers for Disease Control and Prevention issued a warning in early June about increased cases of the virus in the South after a year of low activity. The U.K., France and Japan have also seen a return of RS virus."

"Robert Cohen, a professor at a pediatric research center near Paris . . . said the hygiene measures adopted during the pandemic bring “an immediate and indisputable benefit” because common illnesses have been suppressed. But at some point almost all children are going to get RS virus, chickenpox and viruses that cause colds, which could mean larger outbreaks when the bugs make up for lost time, he said."