Flu (or influenza) is a very common and infectious virus, which infects the nose, throat and lungs and commonly causes coughing, a high temperature, an aching body and feeling tired or exhausted.

 Flu can be much more severe than the common cold, particularly during pregnancy. Serious complications of flu during pregnancy include bronchitis, pneumonia, sepsis (a severe and life-threatening infection of the whole body), meningitis and encephalitis (inflammation of the brain).

When you are pregnant, you are about five times more likely to become seriously ill with or die from flu. Catching flu when you are pregnant may even increase the chance that your baby will be born too soon, and in rare cases flu can lead to the death of the baby before or shortly after birth.

You will be offered a flu vaccine during your pregnancy to protect you and your baby against these problems.

The flu vaccine is available between September and January.

You can have the flu vaccine at the same time as your other pregnancy vaccines, such as whooping cough and RSV, but it’s best to get your vaccine as soon as it is available.

In many areas, your vaccine will be given by your GP practice. However, some hospitals have now set up special 'vaccination clinics' so you can receive your vaccine when attending your routine antenatal appointments. If they have a vaccination clinic at your booking hospital, your midwife will discuss this with you at one of your appointments.

You can also ask your midwife about the flu vaccine at any of your appointments or contact your GP yourself if you haven’t heard from them.

The flu virus changes constantly and new strains circulate every year. That means that the strains circulating this year will be different to any you may have become infected with or been vaccinated against in the past. You will not be protected against this year’s strains. It is important to get an updated vaccine, to ensure that you and your baby are fully protected.The flu virus changes constantly, and new strains circulate every year. That means that the strains circulating this year will be different to any you may have become infected with, or been vaccinated against, in the past and you will not be protected against this year’s strains. It is important to get an updated vaccine, to ensure that you and your baby are fully protected.

To make sure the flu vaccine offers real protection during pregnancy, researchers have looked at its effects in different ways.

In clinical trials (where participants receive either the flu vaccine or a comparison treatment, such as salt water or another vaccine and the rate at which participants catch flu is compared) flu vaccination in pregnancy reduces the chance of catching flu during pregnancy by 50%.

Observational studies (where the rate at which people who are vaccinated catch flu is compared to the rate at which unvaccinated people catch flu in the whole population) estimate that flu vaccination in pregnancy reduces the chance of needing to go to hospital to be treated for flu by 40%.

You will be offered a flu vaccine with the goal of protecting you and your baby against complications of flu during your pregnancy. However, there is also a benefit to your baby after they are born. Clinical trials find that getting vaccinated against flu during pregnancy reduces the chance that your baby will be admitted to hospital with flu by between 39% and 92%. (Other studies: 64%, 45%)

It’s natural to want to feel confident about anything you take during pregnancy. That’s why the flu vaccine has been extensively studied to make sure it’s safe for both you and your baby.

In seven large studies looking at health of hundreds of thousands of people vaccinated during pregnancy and their babies, flu vaccination did not increase the chance of pregnancy loss, pregnancy problems or health problems for babies.

Like all medicines, vaccines can cause side effects, but not everyone will experience them. Common side effects (affecting more than 1 in 10 people) are:

• Pain, redness or swelling at the site of the injection

• Headache

• Muscle pain

• Tiredness

• Loss of appetite

• Diarrhoea

Side effects affecting up to 1 in 10 people are:

• Nausea, vomiting

• Joint pain

• Shivering

• A high temperature

These side effects may be unpleasant if you experience them, but it is important to know that they are not dangerous for you or your baby, and having any of these does not mean that you have caught flu. These side effects can be managed with paracetamol and usually go away within 1-2 days.

Most people who are offered the flu vaccine can have it. The only people who should not have the flu vaccine are those who have had a serious allergic reaction (anaphylaxis) to a previous dose of the vaccine, or an ingredient of the vaccine.

Some inactivated flu vaccines contain small amounts of egg proteins, as the virus is often grown in eggs. The flu vaccine usually offered during pregnancy is not grown in eggs, but in rare cases, when the first-choice vaccine is unavailable, you may be offered a vaccine that contains small amounts of egg protein. Tell the person vaccinating you if you have an egg allergy.

Different kinds of flu vaccines are offered to different groups. You will be offered an inactivated flu vaccine. The active ingredient of this vaccine is flu virus that has been killed so it cannot cause an infection but still allows your immune system to learn what the virus looks like and how to protect you against it.

The other ingredients are:

• Water

• Sodium and potassium salts, used to make the liquid of the vaccine as salty and acidic as body fluids

• Antibiotics, used to stop bacteria from growing in the vaccine

• Formaldehyde, used to kill the virus

• Polysorbate, used to hold the vaccine ingredients together (an emulsifier)

The flu vaccine usually offered in pregnancy does not contain any animal products. In rare cases, when the first-choice vaccine is unavailable, you may be offered a vaccine that has been grown in eggs and contains small amounts of egg protein. Tell the person vaccinating you if you have an egg allergy.

You will not be offered a flu vaccine containing pork or beef products.

Like all vaccines routinely offered in the UK, the flu vaccine does not contain mercury.