Swine Flu Vaccine Side Effects

What is the Swine Flu Vaccine?

The swine flu vaccine was manufactured in 2009 to combat the H1N1 influenza virus strain. It was slightly different from the seasonal flu virus. A few of the genes of the H1N1 virus were present in the flu virus normally found in pigs on North American farms. This led to the name swine flu. The virus spread from person to person, or from contact with a contaminated surface.

A vaccine was developed to build an immunity against the swine flu. Two kinds of vaccines were produced for the 2009 H1N1 influenza virus. One is a flu shot which is administered via a needle. It contains inactivated, or dead swine flu viruses. The second type is a nasal spray. It contains weakened, live swine flu viruses. Both illicit an immune response from the body, creating a defense against any future infections from the H1N1 virus.

Common Side Effects

There are several side effects of the swine flu vaccine. The flu shot has slightly different side effects from the nasal spray. Common swine flu vaccine side effects associated with the flu shot include redness, swelling and soreness at the injection site. A low grade fever is expected, as well. Body aches and nausea are two more side effects of the flu shot.

Common swine flu vaccine side effects associated with the nasal spray include runny nose and headaches. Children are more prone to wheezing and vomiting, while adults may experience sore throat and cough. Muscle aches and fever are two more side effects of the nasal spray.

The side effects usually start soon after receiving the swine flu vaccine and may last one or two days. Then, the symptoms usually dissipate. On rare cases, an allergic reaction may occur.

Allergic Reactions and Thimerosal

In the manufacturing process for the swine flu vaccine, chicken eggs are used to develop the vaccine. Those who are allergic to chicken eggs should avoid the swine flu vaccine because of the risk of an allergic reaction. Also, if there is an allergy to any other component of the vaccine, it should be avoided.

Some of the vaccine preparations contain thimerosal, which is a preservative. The multi-dose vials contain thimerosal to avoid contamination. Neither the single-dose vials nor the nasal sprays contain thimerosal.

Rare Complications

In very rare circumstances, Guillain-Barré Syndrome may arise. It is estimated that 1 in 1 million people taking the swine flu vaccine may develop the condition characterized by nerve damage, muscle weakness and partial paralysis. The possible cause is an overactive immune system which targets nerve cells. A possible risk factor for this complication is the presence of the bacterium Campylobacter jejuni.


1. "General Questions and Answers on 2009 H1N1 Influenza Vaccine Safety." Center for Disease Control and Prevention. https://www.cdc.gov/h1n1flu/vaccination/vaccine_safety_qa.htm