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Infants have surprisingly strong immune systems

Infants may seem to have weak and vulnerable immune systems, but researchers have now demonstrated that this is simply not the case. A new study from Columbia University Irving Medical Center reveals that when it comes to new viruses, babies have stronger immune systems than adults. 

According to the experts, the infant immune system beats the adult immune system at fighting off new pathogens. The research may explain why infants are less affected by COVID-19.

Dr. Donna Farber, a professor of Microbiology & Immunology, explained that while babies are more prone to respiratory illnesses compared to adults, the difference is that babies are seeing these viruses for the first time. 

“Adults don’t get sick as often because we’ve recorded memories of these viruses that protect us, whereas everything the baby encounters is new to them,” said Dr. Farber.

For the investigation, the researchers tested the immune system’s ability to respond to a new pathogen. They collected naïve T cells, which are immune cells that have never encountered a pathogen, from both infant and adult mice. These cells were administered to an adult mouse infected with a virus.

When the cells competed to eradicate the virus, the infant T cells won by a landslide. The experts report that naïve T cells from infant mice detected the virus earlier (at lower levels), proliferated faster, and traveled in greater numbers to the site of infection – rapidly building a strong defense against the virus. 

In a lab experiment, the T cells of human infants performed just as well against adult T cells. “We were looking at naïve T cells that have never been activated, so it was a surprise that they behaved differently based on age,” said Dr. Farber.

“What this is saying is that the infant’s immune system is robust, it’s efficient, and it can get rid of pathogens in early life. In some ways, it may be even better than the adult immune system, since it’s designed to respond to a multitude of new pathogens.”

“SARS-CoV-2 is new to absolutely everybody, so we’re now seeing a natural, side-by-side comparison of the adult and infant immune system. And the kids are doing much better.”

“Adults faced with a novel pathogen are slower to react. That gives the virus a chance to replicate more, and that’s when you get sick.”

The study results also help to clarify why vaccines are more effective in childhood, when T cells are very robust. “That is the time to get vaccines and you shouldn’t worry about getting multiple vaccines in that window,” said Dr. Farber. “Any child living in the world, particularly before we started wearing masks, is exposed to a huge number of new antigens every day. They’re already handling multiple exposures.”

“Most vaccine formulations and doses are the same for all ages, but understanding the distinct immune responses in childhood suggests we can use lower doses for children and could help us design vaccines that are more effective for this age group.”

The study is published in the journal Science Immunology.

By Chrissy Sexton, Staff Writer

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