H1N1 (2009) flu vaccination for pregnant women: frequently asked questions

Pregnant women are considered to be at increased risk of complications from the H1N1 (2009) influenza virus and the Department of Health and Health Protection Agency recommend vaccination against the H1N1 (2009) in this group; at any stage of pregnancy. Although the pandemic is over, the H1N1 (2009) virus is likely to be one of the main influenza strains circulating in the 2010 winter season.  The seasonal influenza vaccine for 2010/11 contains three flu strains one of which is the H1N1 (2009) virus and this is the recommended vaccine for pregnant women.

Why should I have this vaccine when I am pregnant?

Am I still immune if I had the flu last year?

What flu vaccines have been licensed for use in pregnancy?
Which vaccine is recommended in pregnancy in the UK?

What protection does the seasonal flu jab give me?

I have heard the vaccine cause premature birth?

What do we know about the safety of seasonal or pandemic flu vaccine in pregnancy?

Is the preservative used in the vaccine safe in pregnancy?

Am I more likely to catch flu because I am pregnant?

Should I breastfeed if I have the flu?

If a pregnant woman goes to her GP and is told they don't need to be vaccinated what do they do then?

Bibliography

 

Why should I have this vaccine when I am pregnant?

Pregnant women have not routinely been offered seasonal influenza vaccine in the past unless they were in a clinical risk group. However, there is good evidence from North America, Australia and Europe which shows that pregnant women are at an increased risk of severe disease and admission to hospital with the H1N1 (2009) virus.  The risk increases in the third trimester of pregnancy (6-9 months).

Studies from the US have shown that pregnant women are four times as likely to develop serious illness and they are four to five times more likely to be admitted to hospital with swine flu than the general population.

The World Health Organization (WHO) has reported that 7-10% of all hospitalised patients with swine flu are pregnant women and they are more likely to need intensive care when compared with the general population.
In light of this, all pregnant women are being offered the trivalent seasonal influenza vaccine containing the H1N1 (2009) strain of influenza.

Am I still immune if I had the flu last year?

There is usually more than one type of flu in circulation in any year and having had one type of flu will not protect you from another type. Each year the World Health Organisation makes recommendations about the strains to be included in influenza vaccines for the forthcoming winter. The seasonal flu vaccine for 2010/11 contains the H1N1 (2009) 'swine flu' flu strain antigen and the antigens of two other flu viruses that are predicted to be circulating this year. Therefore if you do not have the seasonal flu vaccine you will not be protected from the other two strains that are predicted to be prevalent this year.

What flu vaccines have been licensed for use in pregnancy?

The seasonal influenza vaccine for 2010/11 is licensed for use in pregnancy. It contains vaccine against three flu strains including the H1N1 (2009) virus. The vaccine is grown in eggs, and contains inactivated virus components. It does not contain an adjuvant.

During the pandemic two flu vaccines were licensed for use in pregnancy - Pandemrix® and Celvapan®.

• Pandemrix® is grown in eggs, and contains inactivated virus components. It contains an adjuvant, which boosts the immune response and reduces the dose of virus required, and a preservative (thiomersal). One dose is normally required for protection.
• Celvapan®, is grown on cultured cells (not eggs) and is a whole virus vaccine (it contains all the virus components). It does not contain an adjuvant. Two doses are required for protection.

All three vaccines are made from inactivated virus - they do not contain live virus and cannot cause flu.

The European Medicines Agency (EMEA) has licensed these vaccines for use in pregnant women. In licensing the vaccines, the European regulators gave careful consideration to the increased risk of complications caused by swine flu in pregnant women, the safety record of seasonal flu vaccines and the adjuvants that were used in the pandemic vaccines.

These vaccines are being used for pregnant women in a number of countries worldwide.

Which vaccine is recommended in pregnancy in the UK?

The seasonal influenza vaccine is recommended for pregnancy in the UK.
The pandemic vaccine is only recommended in certain circumstances, for example for women who have an impaired immune system who have not received this vaccine before.

What protection does the seasonal flu jab give me?

The seasonal flu vaccine generates a protective antibody response in your body to the three influenza viruses, including the H1N1 (2009) 'swine flu virus', that are likely to be circulating this winter.  The protection conferred by the vaccine is not 100% so there is still a small risk of catching flu and you should not ignore the signs and symptoms of  influenza even if you have been vaccinated. If you do become infected with influenza the vaccine will protect you from the more severe forms of illness and death.

I have heard the vaccine cause premature birth?

No, the vaccine is perfectly safe. What is true is that influenza infection increases the risk of premature birth, which is why the Department of Health recommends all pregnant women should get vaccinated.

What do we know about the safety of seasonal or pandemic flu vaccine in pregnancy?

There is no evidence of risk from vaccinating pregnant women with inactivated virus vaccines.
The seasonal flu vaccination has been recommended in pregnancy for several years in many countries and has been shown to be safe in all stages of pregnancy.

Reproductive toxicity studies, and experience from other types of vaccines - both with and without adjuvants - have not raise concerns with the use of these vaccines during pregnancy.

Recent trials of both the pandemic flu vaccines which are licensed for use in the UK have shown that they produce the required immune response we expect to work against the virus.  This is expected to be similar to seasonal flu vaccines (when well matched to the circulating strain) at around 70-80%.

Experience with seasonal flu vaccines have shown that changing the virus strain in a vaccine does not substantially affect the safety of the vaccine.

Is the preservative used in the vaccine safe in pregnancy?

Thiomersal is used as a preservative in some seasonal influenza vaccines and in Pandemrix to reduce bacterial contamination.

Expert scientific advice is clear that thiomersal-containing vaccines, such as Pandemrix, do not present a risk to pregnant women or their babies.

In 2004, EMEA concluded that the studies showed no association between vaccination with thiomersal containing vaccines and specific neuro-developmental disorders.

Another more recent study has shown no association between neuropsychological functioning at age 7-10 years and exposure to thiomersal during the antenatal and neonatal periods, and the first seven months of life (Thomson et al, 2007).

Am I more likely to catch flu because I am pregnant?

The risk of catching flu does not depend on whether you are pregnant or not. What is important to know is that a pregnant woman is at more risk from serious illness if she happens to catch the flu.

Should I breastfeed if I have the flu?

You should seek advice from your GP about this. There may be certain measures that need to be taken which you should discuss with a clinician.  Practicing good hand and respiratory hygiene is important.

If a pregnant woman goes to her GP and is told they don't need to be vaccinated what do they do then?

The seasonal flu vaccine is freely available to all pregnant women and should be routinely offered by GPs to any pregnant women unless they have already recently received the seasonal vaccine.

Bibliography

Jamieson D et al (2009) H1N1 2009 Influenza virus infection during pregnancy in the USA. Lancet 2009; 374: 451-458.

Pandemic (H1N1) 2009: Current pandemic risk assessment. European Centre for Disease Control (ECDC)website.

Plotkin SA Orenstein WA and Offutt PA (eds) (2008) Vaccines 5th Edition. Philadelphia WB Saunders Company.

EMEA/COMP/VEG/1194 (2004) EMEA public statement on thiomersal in vaccines  for human use - recent evidence supports safety of thiomersal-containing vaccines.

Thompson WW Price C Goodson B et al (2007) Early thiomersal exposure and neuropsychological outcomes at 7 to 10 years. N Eng J Med 2007; 357:1281-1292.

Back to top

Last reviewed: 7 January 2011