Flu Vaccine and Pregnancy

Influenza

Influenza is a virus that causes an illness that generally lasts for a few days but sometimes can be quite serious and lead to hospitalization and death. Generally persons most susceptible to influenza are older persons, people with chronic diseases and pregnant women. The symptoms of influenza include fever (97%), non-productive cough (94%), runny nose (59%), sore throat (50%), headache (47%), shortness of breath/chills (41%), diffuse muscle aches (35%), vomiting (18%), and diarrhea (12%). The influenza season in the United States occurs from December until April. The peak activity is from late December to Early March. Pregnant women in all trimesters should consider the influenza vaccine. If you have symptoms or a have a close exposure, please contact us immediately as anti-viral therapy started within 2 days has been shown to help prevent severe illness.

Influenza vaccine

The influenza vaccine is not a live vaccine. In other words, there is no chance of contracting influenza by receiving the shot-in-the-arm vaccine. The optimal time for vaccination is between September and mid-November. It takes approximately 1-2 weeks after vaccination for the antibody against influenza to develop and provide protection. The vaccine is needed on a yearly basis due to the virus changing on a yearly basis. This year (2010) the vaccine also covers the H1N1 strain. Studies of healthy young adults have shown the influenza vaccine to be 70 to 90% effective in preventing influenza.

Influenza during pregnancy

Pregnant women are at higher risk of death and injury if they contract influenza during pregnancy. The H1N1 outbreak of 2009 also revealed pregnant women are at higher risk of preterm labor, stillbirth, and miscarriage. Therefore the baby is at risk too if the mother contracts influenza. Studies of thousands of women who have received the vaccine have shown no adverse affects to the baby. Breastfeeding mothers as well can receive the vaccine without any adverse effect to the baby. Breastfeeding mothers who have received the vaccine will pass antibodies to the baby via breast milk that help protect the baby. Because infants less than 6 months cannot receive the vaccine, all care givers of these infants should consider vaccination too; ie dads and siblings.

Risks of vaccination

Less than 1/3 of people who receive the vaccine have some soreness at the vaccination site. Approximately 5-10% of people experience mild side effects such as a headache or low-grade fever for about a day after the vaccination. One of the more serious side effects occurs in people who have severe allergies to eggs. The viruses that are used in the vaccines are grown in hen’s eggs and because of this people who have an allergy to eggs should not receive the influenza vaccine. The evidence linking the vaccine to a severe paralytic illness called Guillain-Barre Syndrome (GBS) is very weak. The chance of getting GBS after the influenza vaccine administration is far less than the chance of getting severe influenza prevented by the vaccine.

Thimerosal

A concern of the multi-dose vaccine is that it contains a small amount of thimerosal. We have the single-use vaccines available for our pregnant patients. They do not contain thimerosal. The multi-dose vaccine contains a small amount of thimerosal, a preservative that contains mercury. The amount is about 25 mcg. The amount of mercury in 6 oz. of white tuna is about 50 mcg. Pregnant women should limit fish and tuna to no more than 2 x per week. Most likely the amount of mercury in the vaccine is not significant. With the increasing incidence of autism, however, it seems prudent to use non thimerosal containing vaccines for pregnant patients and children. If you receive a multi-dose vaccine, it seems reasonable to skip a fish/tuna meal to account for the mercury in the vaccine.

We would not recommend the vaccine if you:

  • Have a serious allergy to eggs.
  • Have ever had a serious allergic reaction or other problem after getting an influenza vaccine.
  • Have ever been paralyzed by Guillain-Barre Syndrome
  • Now have a moderate or severe illness

Symptoms to be on the lookout for after receiving the vaccine include evidence of a severe allergic reaction that would present with hives, difficulty breathing, or shock. If you have any significant side effects after administration of the vaccine, contact our office or the ER immediately.

We hope that this has been helpful in making a decision whether or not to become vaccinated this season with the influenza vaccine. Web resources include: cdc.gov/flu and flufacts.com.

FYI: “FluMist” is a live flu vaccine that a person sprays into their nose. This vaccine is contraindicated in pregnancy. Pregnant women should not receive “FluMist.”

Revised September 2010