Swine Flu Vaccine

Written by Kristeen Moore | Published on July 18, 2012
Medically Reviewed by Brenda B. Spriggs, MD, MPH, FACP

What Is the Swine Flu Vaccine?

The swine flu vaccine is the most effective way to protect yourself from the H1N1 virus which causes a respiratory disease. Swine flu or H1N1 virus first emerged in 2009. A separate vaccine was produced that year because the regular all-encompassing flu shot had already been made when the virus was identified.

Some people are concerned about the safety of the swine flu vaccine because the strain is fairly new. However, the Centers for Disease Control and Prevention (CDC) has deemed the vaccine safe for most people. A swine flu vaccine is the most effective way to protect yourself from the H1N1 virus.

Vaccine Features

Vaccines for viruses such as swine flu usually contain weakened or dead forms of the virus. These cause your body to produce antibodies that will protect you against the virus. About two weeks after being vaccinated against flu, you should have antibodies.

During the 2009 U.S. swine flu pandemic (a world wide infectious disease) the vaccine for the H1N1 virus was offered to the public by itself. Now each seasonal flu vaccine contains the H1N1 strain. These vaccines are generally available between September and May every year.

According to the CDC, each seasonal flu vaccine protects against the three most common types of flu (CDC). At present, swine flu is one of these.

Types of Swine Flu Vaccines

The seasonal flu vaccine with the H1N1 strain comes in two forms: shot and nasal spray.

Most people receive a flu vaccine by getting a shot that contains the inactivated, or killed, viruses. In this form, the viruses do not cause the flu.

There are three versions of this shot:

  • regular intramuscular shot: This is the most common type of flu shot given. It is approved for people age 6 months and older. The shot is given with a needle inserted into a muscle, usually in the arm.
  • high-dose shot: A shot for those 65 and older, it contains four times as much of the inactivated virus to encourage the body to produce more antibodies. This is needed because older adults usually have weaker immune systems and will need more antibodies to fight a flu infection than a younger person, according to the CDC. (CDC)
  • intradermal shot: This shot is given into the skin instead of muscle. It is available for those aged 18 to 64. The needle used to inject the vaccine is much smaller than the one used with the regular shot.

In addition, this shot contains a smaller amount of the killed flu viruses than the regular shot but is just as effective. According to Sanofi Pasteur, the company that manufactures this shot, injecting the vaccine into the skin allows it to reach the dendritic cells, which are important in activating the immune system. (Sanofi Pasteur)

  • A nasal spray: Spray flu vaccine contains low doses of live flu viruses, but they are weakened to the point where you won’t develop the flu. The nasal spray is available for those aged 2 to 49. Sometimes this type of vaccine is referred to as live attenuated influenza vaccine (LAIV).

Because the virus is live and there is a possibility—though very small—that it might cause the flu, you cannot choose the spray method if you have an underlying medical condition that might cause complications with the flu. For example, the CDC doesn’t recommend the nasal flu vaccine for pregnant women.

Pros and Cons

Experts are still working to determine whether there is a difference in effectiveness between the shot and spray. The CDC does not recommend any one method or version over another.

Each method has pros and cons related to potential side effects and your tolerance for needles.

Side effects of the regular and high-dose flu shot are usually minor. You may experience soreness in the injected muscle, as well as a low-grade fever and muscle aches. However, this method uses large needles to deliver the vaccine. The intradermal method may be attractive because using a smaller needle and injecting the skin mean less pain. Side effects of this shot are similar to the others.

Nasal sprays may be preferred for young children or adults who may not want to receive shots. However, this method has the potential for more severe side effects.

Side effects may include:

  • runny nose
  • headache
  • fever (children only)
  • wheezing (children only)
  • vomiting (children only)
  • muscle aches (children only)
  • sore throat (adults only)
  • cough (adults only)

Vaccination Recommendations

Most people should receive annual flu shots, except for infants under six months of age. Young children are most vulnerable to flu-related complications because they haven’t had the opportunity to naturally build their immune systems that adults have. Pregnant women as well as adults over the age of 65 are also vulnerable to swine flu-related complications and should promptly receive vaccines.

If you work with children or the elderly on a regular basis, you should get your flu shot as soon as possible each flu season. The vaccine usually becomes available in September.

Possible Complications and Adverse Reactions

Some individuals may have a bad reaction to the flu shot. Although such reactions are rare, you should avoid flu vaccines if you:

  • currently have a fever
  • are highly allergic to chicken eggs
  • have a history of adverse reactions to flu vaccines


The annual flu vaccine protects against all major flus, including the H1N1 virus. However, this doesn’t mean that there is a 100 percent guarantee you won’t get the flu. Vaccinations take up to two weeks to take full effect. According to the Mayo Clinic, the flu vaccine’s effects are strongest within the six months after taking the shot or spray.

If you don’t feel well, it is best to stay home to prevent the flu from spreading to others. Some symptoms of the flu include:

  • fever
  • chills
  • body aches
  • headache
  • excessive fatigue
  • sore throat
  • cough
  • runny nose

Keep in mind that you may experience only a few of these symptoms. If your condition doesn’t improve within a few days, then you should contact your healthcare provider immediately. According to the CDC, all forms of the flu are contagious one day before you experience symptoms and up to seven days after you get sick.

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