Since 2011 , the HSE recommend pregnant women be vaccinated against influenza during the flu season, October through April. Before 2011, there were no vaccines recommended during pregnancy. There are two inactivated vaccines available:

• Influvac Tetra manufactured Abbot Biologicals
• Quadrivalent manufactured by Sanofi

This article provides an overview of the potential risks associated with both the vaccine and the disease it targets, helping you make an informed decision.

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Disease versus Vaccine Risk Summary

Risk from Influenza during Pregnancy

Risk of admission to ICU during pregnancy

Post vaccine: 16 admissions to ICU between 2012 and 2019
Approx 1 in every 28,000 pregnancies (0.004%) per year

Risk of death from influenza during pregnancy

Deaths in pregnant women are extremely rare. Zero deaths recorded between 2011 to 2020.

Risk from Quadrivalent Influenza Vaccine

(1 dose recommended annually)

Observed side effects post administration of Quadrivalent Vaccine (post marketing)

Pain situated on the nerve route (neuralgia), fits (convulsions), neurological disorders that may result in stiff neck, confusion, numbness, pain and weakness of the limbs, loss of balance, loss of reflexes, paralysis of part or all the body (encephalomyelitis, neuritis, Guillain-Barré syndrome). Blood vessel inflammation (vasculitis) which may result in skin rashes and in very rare cases in temporary kidney problems. Transient thrombocytopenia, lymphadenopathy, paraesthesia.

Risk Category	Potential Side Effects
< 1 in 1,000 (0.1%)	Allergic reaction that can be life-threatening. Anomalies in the perception of touch, pain, heat, and cold (paraesthesia), sleepiness, increased sweating (hyperhidrosis), unusual tiredness and weakness (asthenia), flu-like illness. Joint pain (arthralgia), discomfort at the injection site.
< 1 in 100 (1%)	Dizziness (rare in adults), diarrhoea, feeling sick (nausea – rare in elderly), fatigue, reactions at the injection site: bruising (ecchymosis), itching (pruritus), and warmth. Swelling of the glands in the neck, armpit, or groin (lymphadenopathy).
< 1 in 10 (10%)	Fever (common in elderly), shivering, reactions at the injection site: redness (erythema), swelling, hardness (induration).
> 1 in 10 (10%)	Muscular pain (myalgia), generally feeling unwell (malaise – common in elderly), pain at the injection site.

Some other special warnings and precautions

Do not use Quadrivalent Influenza Vaccine if you are allergic to eggs (ovalbumin, proteins), neomycin, formaldehyde, or octoxinol-9.

Adverse Events on WHO Vigibase Reporting System

As of February 2024, there were 323,599 reports for all influenza vaccines.

Risk from Influvac Tetra Influenza Vaccine

(1 dose recommended annually)

Observed side effects post administration of Influvac Vaccine (post marketing)

Severe allergic reactions occurred occasionally. Skin reactions that may spread throughout the body including itchiness of the skin (pruritus), urticaria, rash. Blood vessel inflammation which may result in skin rashes (vasculitis) and in very rare cases in temporary kidney problems. Pain situated on the nerve route (neuralgia), anomalies in the perception of touch, pain, heat, and cold (paraesthesia), fits (convulsions) associated with fever, neurological disorders that may result in stiff neck, confusion, numbness, pain and weakness of the limbs, loss of balance, loss of reflexes, paralysis of part or all the body (encephalomyelitis, neuritis, Guillain-Barré Syndrome). Temporary reduction in the number of certain types of particles in the blood called platelets; a low number of these can result in excessive bruising or bleeding (transient thrombocytopenia); temporary swelling of the glands in the neck, armpit or groin (transient lymphadenopathy).

Risk Category	Potential Side Effects
Up to 1 in 100 (1%)	Fever
Up to 1 in 10 (1% to 10%)	Sweating, muscular pain (myalgia), joint pain (arthralgia). Generally feeling unwell (malaise), shivering. Local reactions: redness, swelling, bruising (ecchymosis), hardness (induration) around the area where the vaccine is injected.
> 1 in 10 (10%)	Headache, fatigue, local reaction: vaccination site pain.

Some other special warnings and precautions – avoid if

If you are allergic to eggs (ovalbumin, chicken proteins), neomycin, formaldehyde, cetyltrimethylammonium bromide, polysorbate 80, or gentamicin, an antibiotic.

Adverse Events on WHO Vigibase Reporting System

As of February 2024, there were 323,599 reports for all influenza vaccines.

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What is influenza?

Influenza is a viral infection that produces fever, chills, sore throat, muscle aches, and cough that lasts a week or more. People tend to use the term “flu” to describe any kind of respiratory or gastrointestinal illness, such as colds or diarrhoea and vomiting that resemble “influenza-like-illness” (ILI) symptoms. But influenza is usually associated with more severe illness and lasts longer than the common cold and, normally, influenza does not cause vomiting or diarrhoea in adults.

The vast majority of people recover from influenza without any complications and develop immunity to future infection with the same strain or a related influenza strain that may prevent illness symptoms or make illness less severe. There is, however, an increased risk of serious complications and death for the elderly and those with compromised immune systems or who are suffering from diabetes, kidney, heart or neurological disease .

What is the risk of being admitted to ICU with influenza in Ireland?

What is the risk of death from influenza in Ireland?

The risk of death from influenza for all ages in the decade before the vaccine was introduced in 1988 was approximately 1 in 54,000 (0.002%). The majority of deaths were in people over 75 years old.

In the most recent decade, post vaccine, the risk of death for all ages decreased to approximately 1 in 100,000 (0.001%), however, increased to 1 in 419,000 (0.0002%0 for under 5s). Most deaths were over the age of 75. There is no record of any deaths for pregnant women from influenza during this period.

Does the influenza vaccine guarantee protection against influenza?

No. As with all vaccines and as stated on the patient information leaflets, protection from the disease cannot be guaranteed.

There are hundreds of strains of flu. The strains included in the vaccine are the ones that are predicted to be circulating at the time of formulation. In the US, effectiveness was below 40% for eight years out of the last ten.

Vaccine safety data

Like all medicines, vaccines come with side effects, sometimes very serious.

• See disease vs vaccine risk table at the top of the page for list of possible side effects
• For quadrivalent, there is up to 1 in 1,000 chance of allergic reaction that can be life threatening.
• There is a rare risk of Guillain-Barré syndrome following flu vaccination.
• In this study using inactivated influenza vaccine such as Quadrivalent or Influvac, vaccine recipients were 5.5 times more likely to contract a non-influenza respiratory virus than the placebo group.
• As of February, 2024, there were 323,599 reports of adverse events (ADR’s) on the World Health Organisation VigiAccess database for influenza vaccines. Among these ADRs were 1,424 deaths (under general disorders), 7,371 cardiac disorders and 86,299 nervous system disorders (including 4,020 reports of Guillain Barré syndrome). Pregnancy related ADRs included 265 spontaneous abortions, 97 foetal deaths and 58 stillbirths.
• Injury and death from the Influenza vaccines are the leading types of claims submitted to the Vaccine Injury Compensation Program (VICP) in the US and account for more than half of the $5bn compensation paid out since the start of the program in 1988 .

What are the vaccine ingredients?

Vaccine	Ingredients as listed on patient information leaflets
Influvac (flu)	Active substances: Four strains of influenza virus propagated in embryonated chicken eggs Other ingredients: [popup_anything id=”4327″], [popup_anything id=”3626″], [popup_anything id=”3625″], [popup_anything id=”4326″], calcium chloride dihydrate, magnesium chloride hexahydrate and water for injections. May also contain traces of eggs (such as [popup_anything id=”3624″], chicken proteins), [popup_anything id=”2125″], cetyltrimethylammonium bromide, [popup_anything id=”2983″] or [popup_anything id=”3577″], which are used during the manufacturing process
Quadrivalent (flu)	Active substances: 4 strains of influenza virus propagated in embryonated chicken eggs  Other ingredients: [popup_anything id=”4326″], [popup_anything id=”4328″], [popup_anything id=”3624″], [popup_anything id=”2215″], [popup_anything id=”2125″], [popup_anything id=”4329″]