H1N1 Swine Flu Vaccine Fears Addressed – Single vs. Multi-Dose, Adjuvants, Thimerosal and More

H1N1 Swine Flu Vaccine Q&A

with Medical Expert Bruce B. Dan, MD

The questions and concerns continue to swirl regarding the H1N1 swine flu vaccine, and health consumers continue to fear the safety of the H1N1 swine flu vaccine.

Many health consumers are asking if there are adjuvants in the vaccine, should they receive the vaccine if there’s thimerosal, and what’s the difference between a multiple dose (multi-dose) and a single dose.

Others are asking if they have certain health conditions (diabetes, heart disease, lyme disease, bipolar, etc.) should they receive the H1N1 vaccine.

I constructed a series of questions based on information you are looking for and medical expert, Bruce B. Dan, MD, a specialist in infectious diseases addresses your concerns and helps relieve your fears.

Q: (Barbara)

What is the difference between multiple dose H1N1 swine flu vaccine and single dose H1N1 swine flu vaccine?

A: (Bruce B. Dan, MD)

To facilitate shipping large amounts of vaccine to doctor’s offices and clinics, and to provide for more cost effective distribution of vaccines, they are often manufactured in vials that are topped with a rubber-like stopper that allow for multiple withdrawals of vaccine into individual syringes. These “multi-dose” vials are convenient, but in repeatedly inserting needles through the stopper and withdrawing the vaccine into a syringe bacteria can enter the vial and contaminate the vaccine. In order to prevent this contamination, a tiny amount of a preservative, thimerosal, is often added.

There is no need for a preservative in a single dose vaccine, often already prepackaged in a ready-to-inject syringe.

Q: (Barbara)

Can a patient request to have the single dose vaccine given since it doesn’t contain thimerosal?

A: (Bruce B. Dan, MD)

In a normal flu season, a patient may be able to request the type of vaccine he/she receives but with the current shortages a patient may have to take what’s available.

Q: (Barbara)

Is thimerosal harmful?

A: (Bruce B. Dan, MD)

There is no scientific evidence that thimerosal as a preservative in vaccines causes harm. Thimerosal contains mercury and since one type of mercury termed methyl mercury (the kind found in fish, which have ingested it from environmental pollution) is known to cause illness there was natural concern when the public heard the word “mercury.” Thimerosal contains another form, ethyl mercury.

To avoid confusion and controversy, thimerosal was removed from childhood vaccines. The National Academy of Science’s Institute of Medicine reviewed of all data on thimerosal and found no evidence of adverse effects. You should know that the amount of mercury in a dose of vaccine that contains thimerosal is about the same as contained in an average portion of fish.

Q: (Barbara)

There are some states that have suspended its use—they do not want women and infants to receive the vaccine with thimerosal. CA is one of the states, are there any other states?

A: (Bruce B. Dan, MD)

California passed a law restricting the use of thimerosal in vaccines, other states have submitted bills that did not pass. The legislative process is variable and hard to predict.

Q: (Barbara)

What is an adjuvant?

A: (Bruce B. Dan, MD)

An adjuvant is a substance that makes the material in a vaccine stimulate the immune response to the vaccine so it’s possible to use less vaccine and still get protection. Adjuvants can be as simple as mixing some vegetable oil and water to make the vaccine more effective. They are typically used with other vaccines in the United States, including vaccinations for hepatitis A and B, diphtheria-tetanus-pertussis and Haemophilus influenzae type b (Hib).

Q: (Barbara)

Does the H1N1 swine flu vaccine contain an adjuvant?

A: (Bruce B. Dan, MD)

No adjuvants are used in the present H1N1 vaccine. In fact, no flu vaccine approved for use in the United States has ever contained an adjuvant.

Q: (Barbara)

Is the H1N1 swine flu vaccine not suitable for certain people—who shouldn’t get the H1N1 swine flu vaccine?

A: (Bruce B. Dan, MD)

People who have known allergies to eggs or who have an allergic reaction to a flu vaccine previously should not receive the flu vaccine.

Q: (Barbara)

Is the H1N1 swine flu vaccine contraindicated for people with certain health conditions/illnesses such as lyme disease, diabetes, heart disease, cancer, bipolar?

A: (Bruce B. Dan, MD)

People with underlying medical conditions who would be at risk for serious consequences if they were to get the flu (diabetes, cancer, lung disease, etc., should absolutely get the vaccine).

Q: (Barbara)

“Is the H1N1 swine flu vaccine safe?”

A: (Bruce B. Dan, MD)

The vaccine is produced in the exact same way as the annual seasonal flu vaccines, and has undergone additional tests in adults and children.

The most common side effect, like those of almost all vaccines, is some local tenderness and redness at the site of the injection. No serious illnesses have occurred related to receiving the vaccine.

Q: (Barbara)

“Did you and your family get the H1N1 vaccine?”

A: (Bruce B. Dan, MD)

As soon as the vaccine is available, my entire family will get the vaccine.

Please let us know if you have any further questions or concerns.

About Bruce B. Dan, MD

Bruce Dan, MDBruce B. Dan, MD is a specialist in infectious diseases. He is Adjunct Associate Professor of Preventive Medicine at the Vanderbilt University School of Medicine, and Adjunct Professor at the School of Public Health & Health Sciences, University of Massachusetts Amherst, and Chief Medical Officer and Executive Medical Editor for NBC’s Digital Health Network.

Dr. Dan was the Senior Editor of the Journal of the American Medical Association and Director of the AMA’s Department of Scientific and Clinical Affairs. He was the Director of Medical Affairs for the Center for Bio-Medical Communication, Medical Director and Chief Medical Officer for Medcast Networks, Executive Editor and Anchor for Medical News Network, and a founder and later the Senior Medical Consultant for WebMD. In addition, Dr. Dan has guided the development of numerous Web sites, videos, and new media products.

Dr. Dan provides strategic advice to numerous healthcare organizations, associations, and institutions, and he is a nationally sought after speaker and trainer in the field of medical communications and a widely recognized moderator of teleconferences and panel discussions. He has written extensively on the subject of communication, and he has taught more than 30,000 healthcare professionals how to present information more effectively to their colleagues and to the public.

Dr. Dan was the Medical Editor and on-air correspondent for ABC News, Chicago and was the founding Medical Editor and Anchor for American Medical Television on CNBC. He created the JAMA Report, the AMA’s weekly video news release, which is the most watched news segment in television. Dr. Dan was Medical Correspondent and Resident Physician for the award- winning PBS program HealthWeek, as well as the creator and anchor for Medical News Report. His Doctor’s Corner aired nationwide on National Public Radio, and he can be seen daily on The Patient Channel.  Dr. Dan belongs to a number of professional societies, and he is a Fellow of the Society for Behavioral Medicine and Past-President of the National Association of Medical Communicators.

Dr. Dan graduated from MIT in Systems Engineering in the School of Aeronautics and Astronautics, and completed his graduate work in biomedical engineering at Purdue University. He was senior engineer and computer scientist for the Massachusetts General Hospital before being hired by NASA to develop non-traumatic monitoring devices for the space program. Dr. Dan received his MD degree from Vanderbilt University School of Medicine with an internship and residency in internal medicine; later completing postdoctoral fellowships in infectious diseases at Vanderbilt University Medical Center and in computerized medicine at Texas Southwestern Medical Center in Dallas.

Dr. Dan was a member of the U.S. Epidemic Intelligence Service at the Centers for Disease Control and Prevention, and Deputy Chief of the CDC’s Toxic Shock Syndrome Task Force. He received the CDC’s highest award for Outstanding Epidemic Investigation, and the U.S. Public Health Service awarded him its Commendation Medal for his part in discovering the bacteria, toxin, and cause of toxic shock syndrome.

Dr. Dan was named the American Medical Association’s Morris Fishbein Fellow in Medical Journalism and was the University of Chicago’s William Benton Fellow in Broadcast Journalism, the only physician ever to receive that honor. He is a two-time Emmy award winner for his work in television, a 3-time winner of the International Medical Media Award, and the American Medical Writers Association has honored him with the John P. McGovern Award for outstanding contributions to medical communications.

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  1. 1

    “To avoid confusion and controversy, thimerosal was removed from childhood vaccines.” But not removed from the child dose of H1N1, is that correct?

  2. 2

    I want to know if the H1N1 shot is safe for women who are in their second trimester of pregnancy? I was told to get the shot and did but now I’m really scared and worried that I may have made a mistake. Can you please get back to me and let me know if I did the right thing.

  3. 3

    Hi Arly Helm,

    Thanks for your question.

    Dr. Bruce Dan answers your question:

    “All single-dose syringes of H1N1 influenza vaccine including those for children and pregnant women are thimerosal-free, which addresses any concerns people may have about this preservative (inhaler spray vaccine products are also thimerosal-free). The only H1N1 vaccines that contain thimerosal are those that are produced in multi-dose vials (thimerosal is added to the vials to make them safer by preventing bacterial contamination when the vial is punctured multiple times giving the vaccine to multiple people). The pediatric scientific and medical community has looked carefully at thimerosal and determined that there is no evidence that it causes any harm.”


  4. 4

    Hi Rosalind Smith,

    Thanks for question and concerns.

    Dr. Bruce Dan addresses your question and concerns.

    “You’ve actually done the best thing possible for yourself and your unborn child. The H1N1 vaccine is safe when given at anytime during pregnancy. More importantly when you’re pregnant you are at greater risk for serious illness if you contract H1N1 influenza, more likely to be admitted to a hospital, and more likely to die from the infection. When you get a flu shot it not only protects you from influenza but your baby as well. The antibodies your immune system produces in response to the flu shot cross the placenta and protect your baby after birth for several months, which is especially important since infants under 6 months of age who are not eligible to get the flu vaccine. Also good news is that breastfeeding passes antibodies to your newborn reducing the baby’s chance of getting the flu. It’s important to remember that the “flu shot” you got, a vaccine made with killed flu virus, is the one pregnant women should receive. The other flu vaccine, which is made with a live, weakened flu virus and given by nasal spray, is not approved for pregnant women.”

    Please let us know if you have any further questions or concerns.

  5. 5

    I fear getting the flu more than I fear phantom side effects of the vaccine. Once it becomes available, I will definitely line up to get the H1N1 vaccine. Thanks for the great post. 

  6. 7
  7. 8

    Hi Angela,

    Thank you for your question. Bruce, B. Dan, MD, our medical expert answers your question.

    The CDC guidance for receiving the H1N1 influenza vaccine includes,
    “people ages of 25 through 64 years of age who are at higher risk for 2009 H1N1
    because of chronic health disorders or compromised immune systems. Anyone
    with cancer and diabetes would certainly be included in that group.”

    Thank you again for your question and for following Healthin30. If you have any further questions. please let us know.


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