Did pandemic lockdowns stunt kids' immune systems long-term?

The COVID-19 pandemic drastically reduced people's in-person interactions with others as events were canceled and people limited their excursions, and many also practiced social distancing and masked up if they did go out. These moves were intended to control the spread of the disease and were shown to help flatten the curve.  

However, some concerns have been raised about the potential impact of these actions on children's immune systems, and namely, kids' ability to fight infections. But did COVID "lockdowns" and other pandemic-related restrictions actually stunt kids' immune systems? 

On that front, parents should not fear, experts told Live Science. Social distancing did not permanently stunt children's immune systems. Rather, it just delayed young children's exposure to various germs.

"During the COVID lockdown, our children were exposed to far fewer pathogens than they typically are in a normal year," Dr. Sarah Nicholas, an assistant professor of pediatrics-allergy and immunology at Baylor College of Medicine in Texas, told Live Science. 

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Examples of common respiratory viruses that children may be exposed to include respiratory syncytial virus (RSV); the flu, or iNFLuenza; and human metapneumovirus, as well as various viruses that cause the common cold. After such an infection, the body builds up its immune defenses so that it can tackle these pathogens if it encounters the same ones again. 

Social distancing reduced not only the spread of COVID-19 but also that of other respiratory viruses, which tend to spread in similar ways. When these restrictions were lifted, the viruses were free to circulate in the population again. In addition, viruses responsible for causing other types of disease, such as viral gastroenteritis or stomach flu, also began spreading again.