Examining claims of vaccine harm

As the focus of attention turns to the H1N1 outbreak that is now occurring across the country, the public faces an array of information sources that will influence their opinion about vaccination.

There have been many claims and critiques about the H1N1 vaccine and it has become a springboard to envelop other vaccines and vaccination programs within the realm of this criticism.

Where do these claims of harm from vaccines originate? Is there scientific evidence to support these claims? Where should the public look for information that they can use and be confident that what they are reading is valid?

  • Dr. Nora (Noni) MacDonald, MD MSc FRCPC, Professor of Pediatrics at Dalhousie University and Division Pediatric Infectious Diseases at IWK Health Center.  She also is a consultant to the Department of Immunization, Vaccine, and Biologicals of WHO since completion of her term on the World Health Organization’s Global Advisory Committee on Vaccine Safety. Dr. MacDonald has long been recognized in Canada, as an advocate for children and youth health and as a leader in paediatric infectious disease.


4 thoughts on “Examining claims of vaccine harm”

  1. Dear Dr.
    I am a father of two daughters, 17 months and 5 years. I want to do everything I can to protect them so I’ve been reasearching the H1N1 vaccine. Like most, I’m sure, I’ve been using the internet primarily. My question is, can you please tell me how I can see these named doctors stand in frot of a camera and make the claims that this H1N1 vaccine is dangerous and even make the claim that it causes Autisum? How can there be this many doctors believe so strongly that this vaccine is bad and so strongly that they create organizations to fight their fight? I guess what I’m asking is for your personal opinion as to why they don’t see it the way you do? Please, speculation and hypotheses’ welcome.
    Scott (A dad on the fence)

  2. Dear Scott,

    Thank you for your question. I am reminded of a conversation I had with Dr. Ben Goldacre, physician, who writes a column for the Guardian newspaper in the UK entitled Bad Science. He has written a book of the same name that looks at pseudo-science and the entire montage of scientific claims from a host of people and interests.

    In his conversation he brought up exactly what you were asking. How is it that there will usually be a few people who will stand up and refute claims made by other scientists and clinicians? This by the way, is a very healthy phenomenon, as it challenges the people making the claims to support the veracity of them with evidence. The evidence has to be reproducible, derived by established and credible standard investigative methods. It is a means of comparing information on an apples-to-apples level.

    What this means, is that there will always be conflicting information whenever and wherever scientific investigation and research is practiced. It produces very passionate defenses of one’s beliefs that what they have researched is indeed the truth. I do not for one moment criticize them for their courage to stand up and provide their opinion. This really is no different than presenting or publishing a research paper that runs contrary to others. It is simply the medium that the person is using to express their ideas that differs.

    But what has to follow, if evaluation of all the data on the specific topic that fulfills the criteria mentioned above with respect to rigorous investigation, is a systematic review. When a systematic review is done, all the papers on the topic in question are reviewed. These papers must fulfill specific criteria in order for them to be accepted as valid and properly conducted. Indeed, this is the methodology use by one of the most respected independent evaluation organizations in the world, The Cochrane Collaboration.

    So what that implies, is that you may have several papers that may contradict several hundred other papers that say the opposite. If all these papers are considered to be well conducted, then body of evidence would point towards the several hundred papers as being the correct conclusion to date. This is the basis for any investigative endeavor to find answers to specific questions.

    Unfortunately, science becomes politicized. Organizations form to support a particular belief when said group faces opposition on the basis of the known science. What stems from this is an example of confirmation bias. Confirmation bias occurs when someone has a particular point of view and seeks out any information that will support their point of view. They will exclude or reject any contradictory evidence because it upsets their world view. As human beings we all have a tendency to do this. It is not a criticism that somehow various organizations are malevolent. An excellent book on this particular topic and the assessment of risk is Ottawa Citizen journalist Dan Gardner’s book Risk: The science and politics of fear. Please listen to this interview for more in depth evaluation and explanation of how we assess risk and apply it in our daily lives.

    Forgive me if this is getting long-winded. What I am trying to convey is my approach to reviewing medical information as dispassionately as I can and providing it in a format for people to make their own decisions. What I enjoy the most, is when established assumptions are upset by new evidence forwarding our knowledge and understanding of the topic. It is exciting when this happens; it is what science and medicine should be about. But what I do insist on, is that has to be overwhelming evidence produced by different independent investigators using rigorous scientific methods. Should the claims be correct, it should be reproducible by others following the same methodology of the initial investigators.

    So with that being said and in answer to your question, we have to look at the total body of information including that of the physicians that you mentioned. However, the preponderance of information to date is that the H1 N1 vaccine is safe, when one considers how previous flu vaccines have been made and tested, that there has been extensive evaluation of the adjuvant in question in other vaccines, that there have been population studies been done with other vaccines, and that there has been extensive evaluation of the preservative, thimerosal, by every national public health agency.

    I respectfully submit to you that if there is information that refutes this preponderance of evidence so that the weight of this evidence exceeds that that is accepted today, it would have to be considered and incorporated into changing how we think about the topic. That is how science should work.

    I understand you may not have too much time to review all the information but I have included links within this answer that provides some of the background to my line of thinking. The central tenet to my radio show, Sunday House Call, is to provide unbiased information that applies critical thinking to the various subjects, challenges ideas, and presents evidence to my listeners for them to make their own decisions. I do not receive any financial incentive to promote, attack or defend any issue. I respect my listener’s opinions especially when they differ from mine because it gives everyone an opportunity to present their evidence and practice science. It makes for great teaching opportunities.

    I hope that this explanation clarifies things a bit.

    All the best.


    Public Health Agency of Canada – National Advisory Committee On Immunization: Influenza Vaccine

    Thimerosal in Vaccines
    Thimerosal and Vaccine Safety
    Squalene information from FDA site
    Information on opposing voices and the methodology employed
    An Epidemic of fear
    The Cochrane Influenza Resources
    Cochrane review of vaccines and autism claim

  3. Dear Doctor,

    My question is, if their is a shortages in vaccines for H1N1 and my 18 month old needs two shots, how long can she wait in between the shots before the first one is no longer good? Hope you can understand my question. Thanks for taking the time.


  4. Hi Martine,

    Given your child is in the priority list and that the interval between shots is 21 days, it is likely there will be enough vaccine available for the second shot. Further, this is the minimum interval. Usually the seasonal flu shot is given a month apart for the two doses. Given this time frame and that they are ramping up production, you should be good to go.


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