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Home » Flu vaccine study does not show it causes 5.5X more respiratory infections

Flu vaccine study does not show it causes 5.5X more respiratory infections

Last updated on September 27th, 2021 at 10:47 am

The ignorance of the anti-vaccine crowd is so annoying because I have to spend valuable time trying to clear up their myths, tropes, and outright lies. An anti-science website, Health Impact News, recently published an article discussing a flu vaccine study from 2012. I don’t know why it took them this long to use this as an “anti-vaccine” study, but I don’t think keeping up with primary research is high on their list of goals.

I’m going to look at a few of the points the anti-vaccine crowd tried to make, refuting them one by one, by looking at the original article published in the relatively high impact factor journal, Clinical Infectious Diseases. The TL;DR version is that they didn’t get anything right. so, here we go into the fray.

Vaccine double blind study is ethical

Before we dig into the data, let’s just deal with one of the first statements in the Health Impact News (HIN) account of the published article:

While the government in the U.S. continues to resist doing a true study on vaccinated vs. unvaccinated children or adults, stating that such a study would be “unethical”, researchers in Hong Kong have conducted a true vaccinated vs. unvaccinated study on the influenza vaccine.

Whatever these anti-vaccine people want to believe, double-blinded trials ARE unethical, especially with children. That does not mean all studies with children, like retrospective epidemiological studies, are unethical, just double-blind randomized studies that keep one group of children from getting the vaccine.

In a 2013 article about research ethics with vaccines, the author stated that:

The main problem here is, however, that many infections are characteristically only pediatric diseases, or at least, those infections are specially harmful to the youngest.

It is completely unethical to withhold a treatment (including preventative ones) from a child to put them in an experimental “control group.” It boggles the mind to think that these anti-vaccine activists are trying to claim that they’re protecting children, yet, the first thing they want to do is created double-blind trials that put children in harm’s way. I don’t get it.

The Skeptical OB wrote an article about a good way to think about these trials – child car seats:

Do car seats minimize the risk of injury and death of infants?

There never been a controlled randomized double blind study of carseats. Why not? Because it is unethical to randomize some infants to be unbelted in cars simply so we can check how many will be injured and die.

Does that mean we don’t know if carseats reduce the risk of injury and death? Of course not. There are a myriad of statistical investigations that allow us to determine whether carseats reduce injury and death, including large scale population studies, retrospective cohort studies and many others.

If you want to believe that just because this study was approved by an Institutional Review Board in Hong Kong, it means all pediatric vaccine studies are ethical, well, you’d be wrong. But then again, anti-vaccine zealots are not known for their consistent and logical interpretation of ethics, especially in preventing harm to children. A double-blind flu vaccine study in children is simply unethical.

Flu vaccine study – overall criticisms

Let’s get this right up front – this is a tiny study with 69 children in the vaccine group (receiving the trivalent flu vaccine, Vaxgrip, which is not marketed in the USA) and 46 in the placebo group. Let’s just compare that to clinical trials that include hundreds or thousands of children, such as one for the cancer-preventing HPV vaccine. Clinical trials with small numbers have little relevance, other than providing an “observation” point. There are just too many confounding variables that can affect a small study.

And speaking of confounding variables, this article did not discuss them. Were there socioeconomic or other differences between the two groups that could skew the results one way or another? If one is to claim that one group has more respiratory infections without discussing whether they were located in an area with a lot of air pollution or parents that smoke, it’s hard to derive a useful conclusion from the data.

The third criticism of this study is that it followed patients for nearly nine months. That may appear to be useful, but the temporal relationship between the vaccine and other medical events is hard to correlate after a few days, let alone 270 days.

Let’s look at two of the other points that the anti-science crowd at HIN tried to make.

Flu vaccine study – effectiveness

The anti-vaccine writers tried to create a chart that showed how ineffective the vaccine was.

flu vaccine study

Now their chart was complete digestion of Table 3 of the Cowling et al. study. The writers at HIN completely misinterpreted the numbers and tried to make a case that those who were vaccinated were more at risk of flu than the placebo group. They say, “there were a total of 116 influenza cases in the vaccinated group and 88 in the placebo group.” No there wasn’t. Those numbers represent the incidence rate per 1000 person-years of follow-up. They are derived from the observed incidence, but they are tiny.

Furthermore, this investigation was done in 2009, prior to the worldwide H1N1 Pandemic, and the quadrivalent flu vaccine (which included an H1N1 component) was not widely available. Moreover, there were only 3 cases of H1N1 infection in the vaccinated group (out of 69 children), a tiny number. In fact, the number is so small, there was no statistical difference between the vaccinated and unvaccinated groups for the risk of catching H1N1. They intentionally left out the columns that showed the raw data, just to make a point that fails on so many levels.

Additionally, the HIN writers tried to create a clickbait headline by claiming that “people receiving the flu vaccine suffered from other respiratory infections at a rate 5.5 times more than the placebo group!” Remember the raw numbers are incidence rates per 1000 person-years. Only the Coxsackie/echovirus group showed a statistical difference between the vaccinated and placebo groups. The risk is so small and the patient numbers are so tiny, that slight changes in the number of observed respiratory infections can have a relatively large effect on the incidence rate. This is why clinical trials should include thousands of patients so that a random effect doesn’t have an influential effect on the study.

In fact, the authors state,

The increased risk of noninfluenza respiratory virus infection among TIV recipients could be an artefactual finding; for example, measurement bias could have resulted if participants were more likely to report their first ARI episode but less likely to report subsequent episodes, whereas there was no real difference in rhinovirus or other noninfluenza respiratory virus in- fections after the winter influenza season

So observation bias could be one huge issue.

And, as I mentioned above, the lack of understanding of confounding variables could have a large effect in such a small population size. For example, a family that smokes tobacco products can be more susceptible to respiratory diseases, and if there is a bias towards the vaccinated group with smokers, then this data makes no sense. Of course, we don’t know, because they didn’t look at those potential variables.

The real TL;DR version

Let’s look at this study from a meta-level.

  1. This study was cherry picked out of literally hundreds of flu vaccine studies published in the past 20 years or so. How many claim that there’s a broad difference risk of respiratory infections between vaccinated and unvaccinated groups? Not many.
  2. This study does not “prove” that a double blind study is ethical. In fact, randomized, double blind vaccine studies for children are still unethical.
  3. This study is very small, so clinically based conclusions are just borderline useful.
  4. This study included no analysis of confounding variables.
  5. The anti-vaccine biased editors at Health Impact News cherry picked data (and then completely misused it) out of a cherry picked article. Cherry picking the cherry picking is a whole new level of logical fallacy.

So, no. This flu vaccine study does not say that vaccinated individuals are 5.5 times more like to get a respiratory virus. I contend this study doesn’t tell us much at all.


Michael Simpson

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