Need to talk? Call 1800 882 436.
It's a free call with a maternal child health nurse. *call charges may apply from your mobile

Is it an emergency? Dial 000
If you need urgent medical help, call triple zero immediately.

beginning of content

How your baby's immune system develops

8-minute read

Key facts

  • Your baby’s immune system is not fully developed when they are born.
  • The mother’s antibodies last in your baby for weeks or months after birth.
  • 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 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.

FIND A HEALTH SERVICE — The Service Finder can help you find doctors, pharmacies, vaccination clinic's and other health services.

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.

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.

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

Last reviewed: December 2023


Back To Top

Need more information?

Breastfeeding and immunity | Australian Breastfeeding Association

Breastfeeding boosts your baby's immunity. What about vaccinations and can breastfeeding help when my baby has immunisations? 

Read more on Australian Breastfeeding Association website

Influenza (flu) vaccinations - ACT Government

Find out more about flu vaccination in the ACT.

Read more on ACT Health website

COVID-19 vaccination - Better Health Channel

How to book your COVID-19 booster appointment and advice about vaccination.

Read more on Better Health Channel website

Influenza vaccines – frequently asked questions (FAQs) | NCIRS

Influenza is an acute respiratory illness that occurs after an infection with an influenza virus. It is often called ‘the flu’. Find out more frequently asked questions.

Read more on National Centre for Immunisation Research and Surveillance (NCIRS) website

Vaccines: how they stop infectious disease | Raising Children Network

Vaccines help the immune system recognise viruses and bacteria and destroy them quickly. This is how vaccines protect your family from infectious diseases.

Read more on raisingchildren.net.au website

Vaccines during pregnancy - ACT Government

Vaccinations recommended for pregnant people and where to receive these in the ACT.

Read more on ACT Health website

Immunisation and vaccinations for your child

Vaccinations and immunisation protect babies and children. Read more on why and when to vaccinate your child, and about side effects and costs.

Read more on Pregnancy, Birth & Baby website

COVID-19 vaccines: Frequently asked questions (FAQs) | NCIRS

COVID-19 vaccines: Frequently asked questions (FAQs) COVID-19 Australian Immunisation Handbook COVID-19 vaccines Immunisation coverage data and reports Education and training History of immunisation Immunisation schedules National and international resources NCIRS fact sheets, FAQs and other resources COVID-19 DTPa-HB-IPV-Hib vaccine (Vaxelis® and Infanrix hexa®) Haemophilus influenzae type b (Hib) Hepatitis B Human papillomavirus Influenza Japanese encephalitis Measles Measles vaccination catch-up guide Meningococcal Mpox (formerly known as monkeypox) Mumps Pertussis Pneumococcal Poliomyelitis Respiratory syncytial virus (RSV) Rotavirus Rubella Varicella-zoster (chickenpox) Zoster (shingles) Injection site reactions Vaccine components Vaccines for Australian adults Vaccinations during pregnancy NCIRS webinar series Patient communication resources Specialist immunisation services SKAI - supporting health professionals NCIRS newsletters Vaccine safety COVID-19 Australian Immunisation Handbook COVID-19 vaccines Immunisation coverage data and reports Education and training History of immunisation Immunisation schedules National and international resources NCIRS fact sheets, FAQs and other resources COVID-19 DTPa-HB-IPV-Hib vaccine (Vaxelis® and Infanrix hexa®) Haemophilus influenzae type b (Hib) Hepatitis B Human papillomavirus Influenza Japanese encephalitis Measles Measles vaccination catch-up guide Meningococcal Mpox (formerly known as monkeypox) Mumps Pertussis Pneumococcal Poliomyelitis Respiratory syncytial virus (RSV) Rotavirus Rubella Varicella-zoster (chickenpox) Zoster (shingles) Injection site reactions Vaccine components Vaccines for Australian adults Vaccinations during pregnancy NCIRS webinar series Patient communication resources Specialist immunisation services SKAI - supporting health professionals NCIRS newsletters Vaccine safety Key points COVID-19 is a disease caused by the SARS-CoV-2 virus

Read more on National Centre for Immunisation Research and Surveillance (NCIRS) website

Pregnancy and breastfeeding with hepatitis B

Hepatitis B is a virus that damages your liver. Infection with HepB can pass to your baby during birth. Read more on what to do if you are diagnosed.

Read more on Pregnancy, Birth & Baby website

Should I get the COVID-19 vaccination during pregnancy? | Sharing Knowledge About Immunisation | SKAI

Should I get the COVID-19 vaccination during pregnancy? Key facts COVID-19 infection in pregnancy can cause serious illness and complications for pregnant women and their babies

Read more on National Centre for Immunisation Research and Surveillance (NCIRS) website

Call us and speak to a Maternal Child Health Nurse for personal advice and guidance.

Need further advice or guidance from our maternal child health nurses?

Healthdirect Australia acknowledges the Traditional Owners of Country throughout Australia and their continuing connection to land, sea and community. We pay our respects to the Traditional Owners and to Elders both past and present.

This information is for your general information and use only and is not intended to be used as medical advice and should not be used to diagnose, treat, cure or prevent any medical condition, nor should it be used for therapeutic purposes.

The information is not a substitute for independent professional advice and should not be used as an alternative to professional health care. If you have a particular medical problem, please consult a healthcare professional.

Except as permitted under the Copyright Act 1968, this publication or any part of it may not be reproduced, altered, adapted, stored and/or distributed in any form or by any means without the prior written permission of Healthdirect Australia.