Does the Flu Vaccine Work?

There is a photo circulating on Facebook that shows the package insert for a flu vaccine that appears to indicate that the vaccine has not been shown to be effective against influenza. Of course, this has gone viral, (sorry for the pun) especially among the anti-vax crowd.

I wanted to do a little investigating to understand the statement on the package insert. The insert says: “FLULAVAL is a vaccine indicated for active immunization against influenza disease caused by influenza virus subtypes A and type B contained in the vaccine… This indication is based on immune response elicited by FLULAVAL, and there have been no controlled trials adequately demonstrating a decrease in influenza disease after vaccination with FLULAVAL”

Its the last statement that has triggered concern: no controlled trials adequately demonstrate a decrease of influenza disease after vaccination? Sounds bad, so lets take a look. The package insert actually has 14 pages. They show the results from a 2005-2006 clinical study involving 7482 people. About half received the vaccine and half received a placebo. Then they followed those individuals to see who got the flu. 23 people receiving the vaccine got a strain of flu against which the vaccine is supposed to protect. 45 receiving the placebo got those same strains of the flu. The statistical analysis shows a vaccine efficacy of about 46%, but the calculation of the confidence interval suggests the efficacy could be as low as 9.8%. Before doing the clinical study, they decided that the lowest limit of the confidence interval had to be above 35% to be considered successful. So it seems that the statement that clinical trials have failed to show efficacy is correct due to the large error range in their data.

Lets consider the other statement, that FLULAVAL is indicated based on it eliciting an immune response. Data from another study is shown in which people were given the vaccine and after 2 weeks, then checked for production of antibodies. In this study the levels of antibody increased to high enough levels in enough individuals that the vaccine met the criteria for success. Furthermore, they did a test called an Immunological Non-Inferiority test. Basically, they wanted to know if FLULAVAL induces an antibody response that is at least as good (ie not inferior to) another vaccine available on the market, FLUZONE. FLULAVAL induced as good a response as FLUZONE. (If you take a look at the FLUZONE package insert, they only report data on antibody responses, and state that no data is available on whether FLUZONE reduces incidence of influenza).

So there appears to be something of a conflict: the clinical trial was not successful but the vaccine appears to induce an appropriate response. Perhaps the measurement of antibodies is not the ideal indicator for predicting protection? This speaks to an important question in vaccine development, which is determining the correlates of protection. That is, what specific part of the immune response is needed for immunity?

Lets also look at other flu vaccines. FLULAVAL is one of seven different flu vaccines available.
Fluarix: Clinical studies show a reduction in influenza disease in vaccinated vs placebo groups.
FluMist: Clinical studies show a reduction in influenza disease in vaccinated vs placebo groups. The data for FluMist are the most impressive, getting as high as 96% efficacy with certain flu strains.
FluVirin: Only shows immunogenicity data, induces antibody response that exceeds the threshold defined for success.
FLUZONE: Only shows immunogenicity data, induces antibody response that exceeds the threshold defined for success.
Afluria: Only shows immunogenicity data, induces antibody response that exceeds the threshold defined for success.
Agriflu: Clinical studies show a reduction in influenza disease in vaccinated vs placebo groups.

Interestingly, it appears that approval of flu vaccines is based on showing that the vaccine can induce a strong antibody response, not showing that the vaccine prevents the disease.

Package inserts don’t communicate the whole story. We also have to consider the total body of evidence, not just one or two tests. There are many other clinical trials demonstrating the efficacy of flu vaccines. Such as this one, this one, this one, and this one.
In the clinical trials described in the package inserts, the severity of disease is not indicated. Did the vaccinated people get less severe disease than the non-vaccinated people? A vaccine that induces sufficient immunity so that it prevents severe disease although you might still get a sniffle, would still be pretty good. There are other outcomes to consider too. Does the vaccine reduce transmission or complications following influenza disease? In Canada, Ontario made efforts to dramatically increase influenza vaccination, with the result of reduced influenza associated mortality and reduced healthcare use. And take this study in which it was found that vaccination of healthcare workers didn’t reduce incidence of flu in those vaccinated but reduced the mortality rate of their patients.

There is an obvious need for a flu vaccine that induces better protection, especially in children and the elderly, and ideally, one that is universal so we dont have to go every year to get a shot and dont have to depend on predictions of what is going to circulate in the future. But the evidence that the flu vaccine is beneficial for individuals and society is pretty strong. Finally, I think this emphasizes the importance of digging deeper to understand the information around us. It is never as simple as it seems and we must avoid reducing information to the simplest single sentence thus removing the underlying complexities.

Disclaimer: I am “not that kind of doctor” so this is not intended to provide any medical advice or recommendations for which vaccine to use.


10 thoughts on “Does the Flu Vaccine Work?”

  1. “But the evidence that the flu vaccine is beneficial for individuals and society is pretty strong…

    we must avoid reducing information to the simplest single sentence thus removing the underlying complexities.”

    what evidence?

    I personally will never have a flu vaccine or give them to my children … I don’t buy it that extra formaldehyde, mercury or aluminium are safe …
    And I question the agenda of Vassar – on whose payroll?

  2. They still do not show that the ingredients such as mercury and other dangerous substances which may cause toxicity, organ damage, autism, etc. Without these other studies, vaccines should be the last resort. As admitted in the article, some of those given the vaccine contracted the flu. What is missing is that maybe those people would not have, if they remained off the vaccine.

    Even the CDC admits that many came in after the flu shot that contracted the flu that the vaccine was suppose to keep them from.

    If you are in charge of population control, depopulation and you have an avenue to see it happen through war, abortions, “death with dignity” (suicide), etc. Wouldn’t a vehicle like injections help promote your agenda?

  3. Good question. The vaccine is tested simply by measuring whether antibodies are generated in response to the shot. Since it is known that antibodies are protective, then it is fairly safe to assume that the vaccine will protect. Its called a correlate of protection; the presence of influenza specific antibodies correlate strongly with protection, and we know how antibodies work to protect against infection, so their presence should be a sufficient indicator that the vaccine will work. Also, the process of making the vaccine doesnt change, just what specific viruses go into it, so the effectiveness should be similar each time. You are right though that there isnt time to demonstrate in a controlled clinical trial, that the vaccine can prevent disease. Many of those kinds of studies are done afterwards, and show some mixed results but generally show a benefit, as I mention in the blog. THis does emphasize one of the problems with the current flu vaccine approach, in that it would be better if we had a universal vaccine that didnt have to be reformulated so often. That is a major area of research and there is some progress but for now we are stuck with this imperfect approach.

  4. Since the vaccine has to be prepared before the flu season starts, how feasible is it to conduct adequate controlled trials for a particular season’s vaccine by the time it’s being packaged?

  5. Before we make assumptions about what is in the vaccine preparation, you can easily check. Depending on the specific vaccine, many of those ingredients may not be present. Some dont use the mercury containing preservative thimerosal for example. Numerous studies have demonstrated that thimerosal is not harmful anyway. Yes, mercury sounds scary but lost of things do, so the best way to figure out what we do or do ot need to worry about is to do the research. Extensive research has been done on thimerosal and it is not harmful and certainly not associated with autism. Aluminum has also been shown to be safe, and kids are exposed to large amounts of it playing in the dirt, since it is so abundant in soil, without effect. In the package inserts I checked, there was no aluminum. Formaldehyde is present in some, in varying amounts. Formaldehyde also sounds nasty. But it turns out that there is always some formaldehyde in our body due to the fact that it is an intermediate in several metabolic process involved in making DNA and protein, something our cells do all the time. There is about 10 times as much formaldehyde circulating in the blood of a baby as there is in a vaccine.

  6. What about all the materials that are included in the vaccine such as mercury, aluminum, formaldehyde, etc… that can harm children and vulnerable others?

  7. What you don’t cover is all the other materials/crap in the vaccines such as formaldehyde, aluminum, mercury, etc. and what they can do to children and vulnerable others.

Comments are closed.