Should Anorexia Nervosa Patients Get the Flu Shot?

Is getting the flu shot a good idea if you have anorexia nervosa? Is it safe?

To be honest, I’ve never asked myself that question before. Last year, when I was underweight, I got a flu shot mainly because the laboratory where I am doing my graduate degree is in a hospital–the same hospital that was at the centre of the SARS epidemic in Toronto–and I didn’t want to put patients at risk. Sure, I spent most of my time staring at worms through a microscope (true story) but in the rare event I ventured outside for a coffee, I didn’t want to cough on newborn.

So I was kind of excited to find out the answer when someone asked me this question earlier today on tumblr. As expected, I didn’t find much information, but I did find one relevant paper published online in 2011 by Arne Zastrow and colleagues. I thought I’d make a quick post about it to make the information available to others.

As you probably know, getting the flu vaccine is especially important for individuals who are at a greater risk of developing serious complications from the flu. This includes [taken from here]:

  • people with weakened immune systems
  • young children
  • the elderly
  • pregnant women
  • family members and those who provide care to people in the groups listed above should also get the flu vaccine to protect themselves and those around them.

Several studies have suggested that AN patients may have a weakened immune system (immunodeficiency) (Allende et al., 1998; Birmingham et al., 2003). (This deficiency seems to be restored to normal following weight restoration.)

However, the immunodeficiency, if present, is probably not as simple as what would result from typical malnutrition because AN patients probably tend to restrict carbohydrate and fat-rich foods, but still eat protein-rich foods, fruits and veggies. At least this is the hypothesis was used to explain findings in a 1983 study where the immune response, based on several parameters evaluated in the study, was normal in AN patients (Dowd et al., 1983).

Following from this, it would seem that getting the flu vaccine is even more important for anorexia nervosa patients than for their healthy counterparts.

Zastrow et al evaluated nine AN patients (10, but one was excluded) prior to, and following the vaccination, to see how their immune responses measure up to what’s published in the literature for normal weight individuals. Note, this is a pilot study: it is not controlled and it is small.

Zastrow et al - 2012 - Table 1 Adapted

The authors also observed moderate decrease in the number of white blood cells (leukopenia) and red blood cells (erythropenia) in two and three patients, respectively. Two patients had a moderate increase in the number of platelets (thrombocytosis).

So, what happened after the vaccinations? Well, not much. Antibody counts went up, as expected, and were comparable to age-matched healthy controls (from previous studies in the literature). None of the patients experienced any moderate or severe side-effects, and no booster-vaccinations were needed.

The authors write,

In accordance to our findings, a review of available data dealing with malnutrition and vaccination effectiveness draws the preliminary conclusion that ‘malnutrition has surprisingly little or no effect on vaccine responses (Savy et al., 2009).

Keep in mind, this is a small sample size, and as the authors point out, “vaccination efficacy was not assessed.” That is, it is impossible to know whether getting the vaccines prevented any of these participants from contracting the flu. We’d need to know a much larger, properly controlled study, to see that. But it is interesting, and important, to see that despite the low BMI values and for some, a long history of AN, vaccination against the flu evoked the same immune response as it would in healthy controls.

The authors summarize by stating that the flu vaccine (influenza A H1N1 vaccination) in adult anorexia nervosa seems as safe as it in a healthy population, and as such, “recommendable.”

As always, we shouldn’t make any big sweeping conclusions from one study of nine patients, but the findings in this study are positive and encouraging. It will be interesting to see more studies evaluating the safety and effectiveness of other vaccines in anorexia nervosa patients. And by the way, I’m not a doctor, not training to be a doctor, do not want to be a doctor, not an immunologist, did not study immunology in-depth in undergrad, etc.., so don’t make any serious decisions about your health based on what I wrote here, okay. Just sayin’. It should be obvious by now but sometimes it is useful to repeat it.

I’d like to thank the person who asked me this question today! It was fun to research and read about (and review some immunology “basics” I had once learned and quickly forgotten.)


Zastrow, A., Schnitzler, P., Eckerle, I., Herzog, W., & Friederich, H.C. (2012). Immunogenicity and safety of H1N1 vaccination in anorexia nervosa–results from a pilot study. The International Journal of Eating Disorders, 45 (1), 146-9 PMID: 22170028


Tetyana is the creator and manager of the blog.


  1. Having almost been hospitalised this year with a particularly nasty case of influenza, I’ve been told that it’s very important for me to be immunised each year. I dropped a significant amount of weight very quickly, just dipping into the anorexic range despite having ‘insurance’ weight on me and, oh boy, I felt SO MUCH BETTER eating very little and being smaller. It was like a magic bullet for my treatment-resistant depression, not just mood-wise but in terms of cognitive and everyday functioning too. The real Sam was back. I miss her.

    I re-fed myself before I fell back down the rabbit hole, but must admit that I now feel even more depressed knowing that there is a ‘treatment’ (restriction) which works for my depression, but that it’s something which I cannot have. I was sorely tempted not to fight it for that reason, and I’ve been in remission from AN for almost a decade.

    It is clear to me just how easily illnesses like influenza, gastro, etc. can suck you back into AN. Perhaps this is reason enough to be immunised.

    • Sam, thanks for your comment!

      It is important for everyone to getting flu vaccines, but particularly for those at higher risk of averse outcomes if they were to get the flu. I think I should about it more in terms of medical complications, but your story illustrates the other reason why it is important: relapse prevention. Being sick is often really difficult for someone in recovery because it screws up our appetites, making eating properly even *more* difficult. At least that is what I’ve experienced, anyway (rejoicing when I was sick as it was a “valid” reason not to eat as much as I should.)

      “It was like a magic bullet for my treatment-resistant depression, not just mood-wise but in terms of cognitive and everyday functioning too… I re-fed myself before I fell back down the rabbit hole, but must admit that I now feel even more depressed knowing that there is a ‘treatment’ (restriction) which works for my depression, but that it’s something which I cannot have.”

      I think this is a very important point is often overlooked. Hugely important. I think a lot of people can relate to that. I’ve seen many times online people writing that anorexia takes away their depression (at least for a while).

      I used to find restriction very rewarding as well, and there were times before when I felt truly sad–as if I had lost a friend–when I realized that I really can’t starve myself to good, positive, energized (oddly to some, but not really odd), etc.. I often wished it was a viable solution, but unfortunately, it isn’t.

      Thank you for sharing that, Sam. Your comment is very thoughtful and makes me want to see if I can expand on that idea of restriction alleviating depression more.


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