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Is the H1N1 Swine Flu Vaccine Safe?

Get the Facts


Updated October 15, 2009

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Is the H1N1 Swine Flu Vaccine Safe?

A young boy gets a shot

Photo © CDC/PHIL

Many people have expressed concerns over the safety of the new H1N1 swine flu vaccine. I've heard reasons ranging from "it's too new," "it's not tested" to "it contains harmful additives" (adjuvants), among other things. The hesitation is understandable: The idea of the H1N1 flu pandemic is a little overwhelming, and you don't know if you really want to subject yourself (or your kids) to a vaccine that may not work. Add to that the fiasco from the swine flu vaccine campaign of the 1970s and the concern makes a lot of sense.

However, if you take the fear and emotion out of it and look at the facts, it's really not as scary as it seems at first. Let's take a look at these concerns and see if the H1N1 swine flu vaccine is safe.

Concern #1: "It's a Brand New Vaccine and I Don't Want to be a Guinea Pig"

This is really only partially true. It is a new vaccine because it contains a new virus - the pandemic H1N1 influenza A virus. However, it is made just like the seasonal flu vaccine. And changing the strains of influenza in the seasonal vaccine isn't unusual either - they do it every year! The main reason there is a separate vaccine for the pandemic flu is because the seasonal flu vaccine for this year had already been developed when the pandemic started, so it was too late to include this new pandemic strain in the seasonal shot.

Concern #2: "It Hasn't been Tested"

This isn't true. The H1N1 swine flu vaccine has gone through months of testing which found it to be both safe and effective. Plus, it is essentially the same as the seasonal flu shot which has been used for years and is known to be safe.

Concern #3: "It Contains Adjuvants"

The flu vaccines in the United States do not contain adjuvants. Adjuvants are used in some vaccines in other countries to "boost" the vaccine in hopes that they will provide better protection against the virus. But they aren't used in any vaccines in the U.S, so there is no need to be concerned about them.

Concern #4: "It Contains Thimerosal"

Some people also are concerned about vaccines that contain thimerosal. Only the flu vaccine that comes in the multi-dose vial contains thimerosal (it is used as a preservative and protects against contamination) and if you do not feel comfortable receiving it, or allowing your children to have it, there are other options available. The H1N1 vaccine will be available in both the nasal spray form and in single dose vials -- neither of which contain thimerosal.

Concern #5: "The 1976 Swine Flu Vaccine Did More Harm than Good"

It's true that the swine flu vaccine that was administered in the late 70s caused a lot of problems, such as a significantly higher rate of Guillain Barre syndrome, and it turned out that it was unnecessary because the swine flu did not turn into the pandemic that people feared it would. However, this is different not only because H1N1 is already a pandemic, but also because the vaccine is manufactured in a completely different way than the one in 1976 was.

The Bottom Line

Because the H1N1 swine flu vaccine is made in the same way that the seasonal flu vaccine is made, it is not recommended for those with severe egg allergies or an allergy to any other substance that is present in the vaccine. If you have such an allergy, you may want to discuss the use of antiviral medications with your healthcare provider to protect yourself from the flu.

But for everyone else, don't let rumors and myths influence your decision. If you are considered high risk for H1N1 swine flu and are unsure if you should get the vaccine, it is very important to discuss it with your healthcare provider. Don't take chances with your health.


"Questions & Answers: 2009 H1N1 Influenza Vaccine" H1N1 Flu 05 Oct 09. Centers for Disease Control and Prevention. 10 Oct 09.

"General Questions and Answers on Thimerosal" H1N1 Flu 14 Sep 09. Centers for Disease Control and Prevention. 10 Oct 09.

"General Questions and Answers on 2009 H1N1 Influenza Vaccine Safety" H1N1 Flu 05 Oct 09. Centers for Disease Control and Prevention. 10 Oct 09.

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