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A better flu shot for the elderly? High dose flu vaccine as a breakthrough?

By Andy Lazris, MD
December 21, 2014

Should high dose flu shots be used in the elderly?  The New York Times said it best, mirroring the chorus of praise in the press after a major study evaluated the efficacy of high dose flu vaccine in the elderly compared to standard dose: “Now a study, published recently in The New England Journal of Medicine, finds that Fluzone High-Dose does indeed prevent influenza in older adults, reducing cases of the flu by 24 percent compared with the standard version.”

At a facility where I serve as medical director, a resident emailed and accused me of threatening the health of every resident in the community by offering them standard dose flu vaccine instead of high dose. She even said that she had the flu as a result, even though her symptoms preceded the first case of influenza in the state. She further stated that her husband’s doctor, an infectious disease expert, stated that high dose flu vaccine should be given to all elderly people. Essentially high dose flu vaccine, which is fully covered by Medicare, packs more antigen into every flu shot, leading to more antibody response, although not covering any more strains of flu than standard dose flu vaccine. And NEJM did show a sizable 24% reduction in flu among people over age 65 who took high dose vaccine vs. standard dose.  Pretty much a no-brainer to give the high dose shot, right?

Of course, 24% is relative risk, a meaningless parameter that virtually every newspaper, and so many doctors in academic medicine, use to show an exaggerated effect of medical interventions. What is the absolute improvement with the high dose flu shot?  In fact, it is much less impressive. 1.9% of people receiving the standard dose shot developed influenza, while 1.4% of people receiving high dose vaccine developed influenza. That means that 5/1000 fewer people developed flu with high dose vs. standard dose shot, hardly a number worthy of the praise being thrust on high dose vaccination.

Also, given how few people developed flu at all, the difference is relatively meaningless and possibly impacted by chance. In addition, fewer people receiving high dose flu vaccine developed serious side effects (8.3% vs 9%, a difference of 7/1000), something that makes no medical sense and also likely the result of chance rather than any meaningful safety improvement with higher dose flu vaccine that should, if anything, cause more adverse reactions. Of course, the press did not comment on any of these realities.

What does all of this mean? First of all, despite the touted 24% risk reduction with high dose vaccine, this translates into a tiny and clinically insignificant absolute improvement with high dose vaccine that may be related to random chance. Second, very few older people developed flu with either vaccination; if there had been a placebo arm of the study, outcome may not have been very much different than either treatment arm. Third, there is no data about the severity of flu in either arm, or if there was a threat to life in those who developed flu. Fourth, both arms had a very high incidence of serious side effects, far higher than any positive impact the shots had on flu prevention. One wonders how effective any flu shot is in preventing medical complications in the elderly compared to its effect in inducing medical complications that are potentially severe.  Overall, when this study is evaluated through a lens of common sense, high dose flu shots do not improve meaningful health outcomes in the elderly, can induce serious side effects at an alarmingly high rate, and (in my opinion) should not be used until more data is available.

We are quick to leap to conclusions that our medical interventions have a tremendous impact on our patients; the truth is almost always much less impressive when absolute risk/benefit is used, and the complications of the intervention (which is this case were barely mentioned by the press) are almost always more than stated. We have to be very careful about misleading people with such faulty proclamations, or the woman who accused me of threatening the health of an entire community by not using an intervention with no proven efficacy will be pushed to reach conclusions that are both false and potentially dangerous.

A better flu shot for the elderly? High dose flu vaccine as a breakthrough. Or not? What do you think? Tell us in our comments section.

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