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Do babies have weak immune systems


Infant Immune Systems Are Stronger Than You Think

New study may help explain why infants are less affected by COVID than adults

December 10, 2021

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As any parent knows, infants are prone to getting respiratory infections.

But a new study shows that the infant immune system is stronger than most people think and beats adults at fighting off new pathogens.

The infant immune system has a reputation for being weak and underdeveloped when compared to the adult immune system, but the comparison isn’t quite fair, 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.

Watching T cells react to flu antigens helped the researchers identify why naive T cells from infant mice (shown above) responded faster and more robustly to the pathogen than the same cells from adult mice. The colors in the images represent different molecules involved in T cell activation. Images from the Farber laboratory/Columbia University Irving Medical Center.

Babies do get a lot of respiratory illnesses from viruses, like influenza and respiratory syncytial virus, compared to adults. But unlike adults, babies are seeing these viruses for the first time. “Adults don’t get sick as often because we’ve recorded memories of these viruse, and the memories protect us,” Farber says, “whereas everything the baby encounters is new to them.”

In the new study, Farber and colleagues leveled the playing field and only tested the immune system’s ability to respond to a new pathogen, essentially eliminating any contribution from immunological memories.

For the head-to-head comparison, the researchers collected naïve T cells—immune cells that have never encountered a pathogen—from both infant and adult mice. The cells were placed into an adult mouse infected with a virus.

In the competition to eradicate the virus, the infant T cells won handily: Naïve T cells from infant mice detect lower levels of the virus than adult cells and the infant cells proliferated faster and traveled in greater numbers to the site of infection, rapidly building a strong defense against the virus. A laboratory comparison found similar enhancements among human infant compared to 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,” Farber says. “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.”

That appears to be playing out in the case of COVID. “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,” 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.”

The findings also help explain why vaccines are particularly 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,” Farber says. “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 could lead to better vaccine designs for children.

“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,” Farber says.

References

More information

The paper, titled "Infant T cells are developmentally adapted for robust lung immune responses through enhanced T cell receptor signaling," was published Dec. 10 in Science Immunology.

Donna Farber also is chief of the Division of Surgical Sciences in the Department of Surgery, Columbia University Vagelos College of Physicians and Surgeons, and principal investigator at the Columbia Center for Translational Immunology.

All authors (all from Columbia University unless noted): Puspa Thapa, Rebecca S. Guyer, Alexander Y. Yang, Christopher A. Parks, Todd M. Brusko (University of Florida), Maigan Brusko (University of Florida), Thomas J. Connors, and Donna L. Farber.

This work was supported by the U.S. National Institutes of Health (NIH grants AI100119, AI106697, K23 AI141686, and AI42288) and the Helmsley Charitable Trust. Studies were performed in the Columbia Center for Translational Immunology’s Flow Cytometry Core, supported by NIH grants S10RR027050 and S10OD020056, and the Columbia Stem Cell Initiative’s Flow Core, supported in part by NIH grant S10OD026845.

The authors declared no competing interests.

 

How your baby's immune system develops

How your baby's immune system develops | Pregnancy Birth and Baby beginning of content

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Babies' immune systems are not as strong as those of adults. Breastfeeding and vaccinating your baby will help protect them from a serious illness.

What is the immune system?

Your immune system is a network of cells and proteins that are found throughout your body. The immune system fights germs that cause infection.

Germs such as bacteria and viruses are sometimes described as ‘foreign’. This is because they don’t belong in our bodies. Germs can cause your baby to become sick.

If bacteria, a virus or something foreign gets into your body, the immune system starts to act quickly. White blood cells notice that something foreign has entered your body. The white blood cells make special proteins called ‘antibodies’, and also switch on other parts of the immune system. This is called the ‘immune response’ and it fights the infection.

After antibodies have been made, the immune system can 'remember' the germ or virus. This helps the body to fight the germ more easily next time. This memory is called ‘immunity’.

The immune system in babies

A baby’s immune system is not fully developed when they are born. It gets stronger as the baby gets older. The immune system works throughout our lives fighting germs that can cause disease.

A mother’s antibodies are shared with their baby through the placenta during the third trimester (last 3 months) of pregnancy. The mother’s antibodies help protect the baby from illnesses when the baby is born. The type of antibodies passed from mother to baby depends on the mother’s own level of immunity.

Good bacteria in our gut help our immune system to work well. During birth, these good bacteria are in the vagina and are passed on to the baby. This helps good bacteria to start living in the baby’s gut.

After birth, more antibodies are passed to your baby from the colostrum and in breast milk.

Premature babies

Premature babies do not receive as many antibodies from their mothers as full-term babies. Their immune systems are not very strong. Premature babies have a greater chance of getting sick from germs like bacteria and viruses.

How to boost your baby’s immune system

The immunity that your baby receives from their mother at birth does not last long. It will gradually go away after a few weeks or months.

Babies make their own antibodies. Each time they get infected with a virus or other germ, their immune system starts to work. They make new antibodies that will protect them now and in the future.

But immunity in a baby is not as strong as in adults. And it takes time to fully develop. In the meantime, there are some important things you can do to protect your baby.

Breastfeeding

Breast milk contains many good things to help build your baby’s immune system. These include proteins, fats, and sugars, as well as antibodies and probiotics. When a mother comes into contact with germs, she makes antibodies to help her fight the infection. These are passed to the baby in breast milk. Because mothers and babies usually come into contact with the same germs, the mother’s breast milk can protect the baby.

Breastfed babies have fewer infections and get better more quickly than formula-fed babies. However, for mothers who are unable to breastfeed or who choose not to, infant formula is a healthy option.

Breastfeeding cannot fully protect your baby from life-threatening infections like polio, diphtheria or measles. These diseases are very serious and can make your baby very sick. Fortunately, we now have vaccines that work with the immune system to protect your baby.

Vaccination

Vaccinating your children is the safest and most effective way to protect them against serious disease.

Vaccination causes an immune response in the same way that a virus or bacteria would. But it makes an immune response happen without the child actually getting sick. The vaccine makes your child ‘immune’. If your child catches the real disease in future, their immune system will remember the germ. The immune response will swing into action and fight off the disease, or prevent serious complications.

You can be vaccinated for whooping cough in your third trimester or pregnancy. This helps pass on your immunity against whooping cough to your baby.

You can also be vaccinated against influenza (the ‘flu’) when pregnant. This is recommended at any stage of pregnancy, but should happen before the ‘flu’ season starts. Your antibodies to the flu vaccine are also passed on to your baby.

Your baby’s first vaccines are given at birth, then at 6 weeks, 4 months and 6 months of age. Other vaccines and boosters are given over the first few years of life.

Diet and supplements

Taking antibiotics kills some of the good gut bacteria that are important for immunity. Some people think that probiotics can boost immunity after they have had antibiotics. Probiotics are safe for women to use in late pregnancy and after the baby is born. However, it is not clear if probiotics are useful for children or adults. Talk to your doctor before giving probiotics to your baby.

In most cases, breast milk and formula provide all the vitamins and minerals your baby needs. Giving extra vitamins is not recommended for babies.

Once your baby starts on solids, a range of fresh foods should be enough to keep their immune system healthy. This can include different types of pureed vegetables and fruits. Try to keep breastfeeding at the same time as starting solid food.

Speak to a maternal child health nurse

Call Pregnancy, Birth and Baby to speak to a maternal child health nurse on 1800 882 436 or video call. Available 7am to midnight (AET), 7 days a week.

Sources:
Australian Government Department of Health (Influenza vaccination in pregnancy)

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: May 2022


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