Study: Infant immune systems are better than adults at stopping new viruses

NEW YORK, NY. — Babies often come down with respiratory infections, but research suggests the infant immune system is much stronger than most would believe. Researchers from Columbia University find the infant immune system beats the adult immune system when fighting off new pathogens.

According to the research team, while babies are prone to pathogens like influenza and respiratory syncytial virus, this is mostly because it’s the first time their young bodies are experiencing these viruses.

“Adults don’t get sick as often because we’ve recorded memories of these viruses that protect us,” says Donna Farber, PhD, professor of microbiology & immunology and the George H. Humphreys II Professor of Surgical Sciences at Columbia University Vagelos College of Physicians and Surgeons, in a press release. “Whereas everything the baby encounters is new to them.”

For this latest work, Dr. Farber and her team decided to “level the playing field” between adult and infant immune systems by only looking at immune responses to a new pathogen. That way, adults’ “immunological memory advantages” wouldn’t provide grown-ups with a headstart on stopping the foreign invader.

Infant T cells detect lower levels of a virus and mount a strong defense

The team collected naive T cells — immune cells that have not encountered actual pathogens — from infant and adult mice. They placed the cells inside an adult mouse infected with a novel virus.

The researchers observed infant T cells did a better job of killing the virus than older and more experienced T cells in the adult mice. In addition, the naive T cells from the infant rodents could detect lower virus levels than the adult cells and proliferate at a faster rate. The result was sending a more enormous immune response to infection sites and “rapidly building a strong defense against the virus.” When researchers replicated the study with human adult/infant T cells, they found similar findings.

“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,” Dr. Farber explains. “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.”

Naive T cells could explain children’s COVID-19 vaccination responses

This also appears to be the case with COVID-19. “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,” Dr. Farber says. “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.”

These findings may partially explain why vaccinations are effective among kids. Their T cells are young and ready to produce strong immune responses.

“That is the time to get vaccines and you shouldn’t worry about getting multiple vaccines in that window,” Dr. Farber notes. “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.”

The study is published in Science Immunology.