How your baby's immune system develops

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 your body. Germs can cause your baby to become sick.

If a bacteria or virus gets into your baby’s body, their immune system acts quickly.

White blood cells notice that something foreign has entered their body. The white blood cells make special proteins called ‘antibodies’. They 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 will 'remember' the virus. This helps their body to fight the germ more easily next time. This memory is called ‘immunity’.

What is the immune system like in a newborn?

A baby’s immune system is not fully developed when they are born. It gets stronger as the baby gets older.

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

Your antibodies help protect your baby when it is born. They last in your baby for weeks or months after birth. They can help your baby fight diseases before the first vaccines are given.

Good bacteria in our gut help our immune system to work well. These good bacteria are in the mother’s vagina. They are passed on to the baby at the time of birth. This helps good bacteria to start living in the baby’s gut.

After birth, more antibodies are passed to the baby in colostrum (the first breast milk). Antibodies continue to be passed from mother to baby in breast milk.

Do premature babies have the same immune system as full-term babies?

Premature babies do not get 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.

Vaccinations for parents, family members and carers can help keep a premature baby healthy. Encourage family members and carers to talk to their doctor about booster vaccines.

Premature babies still get their vaccines at the same times as full-term babies.

How can my baby’s immune system be made stronger?

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.

Just like adults, babies make their own antibodies. Each time they get infected with a 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. It takes time to fully develop. In the meantime, there are some important things you can do to protect your baby, like breastfeeding your baby and getting vaccinated.

Why is breastfeeding important for your baby’s immune system?

Breast milk contains many good things to help build your baby’s immune system. These include proteins, fats, and sugars. Breast milk also contains antibodies and probiotics.

When a mother comes into contact with germs, she makes antibodies to help her fight the infection. These are passed to your baby in breast milk. Mothers and babies usually come into contact with the same germs. Breast milk can protect the baby because it contains the mother’s antibodies.

Breastfed babies have fewer infections. They get better more quickly than formula-fed babies. However, some mothers are unable to breastfeed or choose not to. In these cases, 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. They can make your baby very sick. Fortunately, we have vaccines that work with the immune system to protect your baby.

How does vaccination help build immunity?

Vaccinating your baby 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 your baby actually getting sick.

The vaccine makes your baby ‘immune’. If your baby catches the real disease in future, their immune system will remember the germ. The immune response will swing into action. It will fight off the disease or prevent serious complications.

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.

Whooping cough vaccination during pregnancy

A mother can be vaccinated for whooping cough (pertussis) from 20 to 32 weeks of pregnancy.

This helps pass on immunity against whooping cough to the baby. It can protect the baby against whooping cough before the first vaccines can be given.

Grandparents, family members and visitors can also get booster vaccines against whooping cough. This can help protect the baby.

Influenza vaccination during pregnancy

A mother can also be vaccinated against influenza (the ‘flu’) when pregnant.

This is recommended at any stage of pregnancy. It is best if given before the ‘flu’ season starts.

A mother’s antibodies made by the flu vaccine are also passed on to the baby. This happens during pregnancy and in breast milk.

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Can diet and supplements help my baby’s immune system?

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.

Are probiotics useful for immune health?

Probiotics are live bacteria and yeasts. They are found in yoghurt and in some supplements. They can be purchased over-the-counter at a pharmacy or health food store.

Taking antibiotics kills some of the good bacteria in your gut. These bacteria 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 your 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.

Resources and support

The Australian Breastfeeding Association has a information page about breastfeeding and immunity.

You can visit the Department of Health and Aged Care for further information about childhood immunisation.