Influenza Vaccination During Pregnancy | Risks & Benefits

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influenza during pregnancy mom and kid in bed

In Hong Kong, pregnant women are one of the priority groups eligible to receive the influenza vaccination according to The Scientific Committee on Vaccine Preventable Diseases. The Government has introduced free/subsidized flu vaccines for pregnant women to promote vaccination but to also protect pregnant women from the influenza (“the flu”) and its complications.


In Hong Kong, influenza is most common from January to March and July to August. It takes the body approximately two weeks to produce protective antibodies after being exposed to the virus in the form of a vaccine, thus getting vaccinated early will help ensure protection during flu seasons.


There are many questions regarding the flu vaccination during and after pregnancy. Dr. Zara Chan 陳駱靈岫 a Specialist in Obstetrics and Gynaecology clarifies some of the concerns around the safety, risks, and benefits associated with the flu vaccination for both mother and baby.

Is the influenza vaccine recommended for pregnant women?

Yes, pregnant women are recommended to get vaccinated for the flu at any stage of pregnancy due to a number of complications that can come from contracting the flu.


Changes in the immune system during pregnancy puts pregnant women at higher risk of contracting infections and suffering from more severe complications of such infections leading to increased risk of hospitalization. The risk continues into the early postnatal period and vaccination can significantly reduce a women’s risk of contracting severe flu infections.


Being vaccinated in pregnancy also helps to protect the baby after delivery as the mother’s protective antibodies will pass to the baby whilst the baby is still inside the uterus and also via breastmilk after the baby is born.


Although uncommon, severe flu complications is associated with premature birth, low birth weight, and stillbirth.

What kind of influenza vaccine can I get?

Pregnant women are advised not to get the nasal spray vaccine (FluMist) which is available in Hong Kong. The injection/shot version is recommended as it is made from an inactivated virus which is much safer for both the mother and the baby at any stage of pregnancy.

What are the common side effects that pregnant women may experience?

The side effects are no different from the ones that affect other people. Symptoms include soreness, redness, or swelling at injection spot, fainting, headache, fever, muscle aches, nausea, and fatigue, symptoms are generally mild and last for 1-2 days.


It is important to note that flu shots can also cause a serious allergic reaction to the vaccine ingredients, particularly eggs.

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People with egg allergies are recommended not to get vaccinated, does this apply to pregnant women?

The main allergy concern with the flu vaccination is an allergy to eggs. Where most people who have an egg allergy can get vaccinated there are some precautions that are made. Those who have a severe life-threatening allergy to egg protein are advised not to get vaccinated, including pregnant women.
This question should be changed to “are people with egg allergies recommended not to get vaccinated?”
The answer is: The CDC (Centres for Disease Control and Prevention) still recommends populations at high risk of flu, such as pregnant women, to get vaccinated despite egg allergies. There are specific guidelines your doctor will know of regarding how and when to give the vaccines to minimize allergic risk.

Is there a risk of having a miscarriage when I get the flu vaccine?

There are numerous scientific studies that show there is no increased risk of spontaneous miscarriage for women who have received the flu shot during pregnancy. Although the data is more limited in the first trimester, the CDC recommends flu vaccinations throughout all trimesters of pregnancy.

Is the vaccine safe? What studies have been conducted by the Centers for Disease Control and Prevention (CDC)?

“Flu shots have been given to millions of pregnant women over many years with a good safety record. There is a lot of evidence that flu vaccines can be given safely during pregnancy; though these data are limited for the first trimester.” – CDC


The CDC conducts safety monitoring of vaccines in general and during pregnancy each flu season. Findings are recorded in the Vaccine Adverse Event Reporting System (VAERS), anyone can report side effects however the reports only indicate whether further investigation is needed. The CDC also conducts research studies via the Vaccine Safety Datalink (VSD). Here are some of the relevant studies in regard to the vaccination during pregnancy and postnatal:


There is no evidence to suggest that complications or birth defects are linked to flu vaccinations and pregnant women. Review the studies here and here.


There is no increase in the risk of miscarriage among pregnant women who received the vaccines in 2005-06 or 2006-07 flu seasons, see the study here.


A large study using VSD data found no increased risk of health issues such as chorioamnionitis, pre-eclampsia or gestational diabetes for women who received the vaccine from 2002-2009 when compared to non-vaccinated women. See the study here.


In regard to premature delivery or low birth weight, a VSD study conducted from 2004-05 and 2008-09 flu seasons between an equal number of pregnant women who did and did not receive the vaccine found no differences between the groups, see the study here.


A large study conducted in 2017 found no increased risk of children with birth defects for women who received the vaccine in the first trimester of pregnancy.


Other relevant studies from the CDC can be found here.

Can women who breastfeed or intend to breastfeed get vaccinated for the flu?

Yes, it is recommended that women who are breastfeeding get vaccinated not only to prevent them from contracting the flu but also to avoid passing the flu onto the baby. 

Children younger than 6 months old cannot receive the flu vaccine, thus they are protected by antibodies transferred to them via the mother inside the uterus and through breastfeeding.

What happens if I contract the flu while pregnant, what can I do?

If you are experiencing flu symptoms talk to your doctor as soon as possible. Early treatment is particularly important for women who are pregnant, a doctor can prescribe antiviral drugs which work 48 hours after symptoms start. Antiviral medication can make the illness milder and can prevent serious health problems associated with the illness. If you have a fever, it is recommended to treat it with paracetamol or an equivalent while contacting your doctor immediately.


To learn more about the Hong Kong government subsidized influenze vaccine for pregnant women, read The Complete Guide to Flu Vaccination in Hong Kong.

Dr. Zara Chan 陳駱靈岫 is a Specialist in Obstetrics and Gynaecology, practicing at OT&P Healthcare’s Woman and Child Clinic in Central. Dr. Chan is Canadian and completed her medical training at the Prince of Wales Hospital in Hong Kong. She received her specialist qualification from the Hong Kong College of Obstetricians and Gynaecologists and is a member of the UK Royal College of Obstetricians and Gynaecologists. She was an honorary lecturer at The Chinese University of Hong Kong and is currently the president of the Midwives and Maternal-Child Caregivers Association.

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This article was independently written by Healthy Matters and is not sponsored. It is informative only and not intended to be a substitute for professional medical advice, diagnosis or treatment. It should not be relied upon for specific medical advice.

Dr. Chan Lok Zara
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