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How your baby's immune system develops

4-minute read

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?

The immune system is a network of cells and proteins that defends the body against infection.

If bacteria, a virus or other foreign substance enters the body, white blood cells identify it and produce antibodies and other responses to the infection. They also 'remember' the attack so they can fight it more easily next time.

A baby’s immune system is immature when they are born. It develops throughout life as they are exposed to different germs that can cause disease.

The immune system in babies

Antibodies are passed from mother to baby through the placenta during the third trimester (last 3 months of pregnancy). This gives the baby some protection when they are born. The type and amount of antibodies passed to the baby depends on the mother’s own level of immunity.

During birth, bacteria from the mother’s vagina is passed on to the baby. This helps to build the colony of bacteria in the gut that contributes to their immunity.

After birth, more antibodies are passed on to the baby in colostrum and in breast milk. But babies’ immune systems are still not as strong as adults’. Premature babies are at greater risk of infection because their immune systems are even more immature and they haven’t had as many antibodies passed to them from their mothers.

Babies produce their own antibodies every time they are exposed to a virus or germ, but it takes time for this immunity to fully develop.

The passive immunity passed on from the mother at birth also doesn't last long and will start to decrease in the first few weeks and months after birth.

How to boost your baby’s immune system

Each time your baby gets sick, they are developing new antibodies that will protect them in the future. In the meantime, there are some important things you can do to protect your baby.

Breastfeeding

Breast milk contains many elements that support your baby’s immune system. These include proteins, fats, sugars and antibodies and probiotics. When a mother comes into contact with germs, she develops antibodies to help her fight off the infection. These are passed to the baby in breast milk. As mothers and babies are usually exposed to similar germs, this means the baby is protected.

Breastfed babies have fewer infections and get better more quickly than formula-fed babies. However, breastfeeding cannot protect your baby from serious, life-threatening infections like polio, diphtheria or measles. Also, for mothers who are unable to breastfeed or who choose not to, infant formula is a healthy alternative.

Vaccination

Vaccinating 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. It means that if your child comes into contact with the real disease in future, their immune system will recognise the germ and respond fast enough to fight off the disease or prevent serious complications.

Pregnant women are vaccinated for whooping cough in their third trimester so they will pass on immunity to their babies.

Your baby will have their first vaccinations at birth, then some more at 6 weeks, 4 months and 6 months and for the first few years of life.

Diet and supplements

Taking antibiotics can kill some of the gut bacteria that are important for immunity. Probiotics are often suggested as a way of boosting babies’ immunity after they have had antibiotics. Probiotics are safe to use in late pregnancy and after the baby is born. However, the evidence is mixed about if they have benefits for children or adults. Talk to your doctor before you consider giving probiotics to your baby.

In most cases, breast milk and formula provide all the vitamins and minerals your baby needs. Additional vitamin supplements are not recommended for babies.

Once your baby starts on solids, a variety of fresh foods including different types of pureed vegetables and fruits should be enough to keep the immune system healthy. Try to keep breastfeeding while you’re introducing solid food.

Call Pregnancy, Birth and Baby on 1800 882 436 to talk to a maternal child health nurse.

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

Last reviewed: July 2019


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