September 24th, 2009
Currently, influenza vaccines come in two flavors: nasal and injectable. The nasal vaccine is a live, attenuated vaccine. This means that the virus, while still “alive”, has had its cellular machinery crippled so that it won’t cause a whole body infection. The injectable vaccine is inactivated, or killed. It is wholly incapable of causing infection.
The nasal vaccine is very popular in our office. I guess people get enough shots around here, already. Based on a study which came out today in the NEJM, I may be rethinking how I recommend different vaccines.
This study looked at healthy volunteers aged 18 to 49 years. A very important point is that none of these individuals had a condition for which vaccine was explicitly recommended, i.e. healthcare workers, asthmatics, very old, very young, etc. In this study population, the inactivated, injectable vaccine was clearly better at preventing influenza. It wasn’t even close. Rates of infection were 3.5% for the injectable vaccine, 7% for the nasal vaccine, and 11% for placebo.
This study is important in answering which vaccine young, healthy individuals should receive. Results from other studies looking at outcomes in asthmatics have suggested that the nasal vaccine may actually be more effective at preventing influenza related exacerbations. Clearly, this is an important question that needs more data to make a definitive answer.
I got my flu shot BTW
Dr. O
September 16th, 2009
Did you know that elite swimmers have a higher prevalence of asthma than other athletes? Surprisingly, this fact was only confirmed in a study relatively recently. Chlorine was an obvious candidate to explain this finding and over the last decade, evidence has been mounting to suggest that water chlorination does indeed lead to an increased risk of developing not only asthma, but allergies as well.
Initially, the problem was blamed on trichloramine, the gas that gives indoor pools their characteristic smell. Once it was discovered that outdoor pool exposure was as bad as indoor pool exposure, then the focus shifted to chlorine products in the water or vapors present around the water surface.
A recent study from Belgium published in the journal Pediatrics looked at three groups of adolescents, two of which had utilized only chlorinated pools and one of which utilized a pool decontaminated by means of a copper/silver ionizer. I read the study in detail and it is very complicated and has some potential holes. Nevertheless, I think it does clearly demonstrate that kids who spend a large amount of time in a chlorinated pool are more likely to develop asthma and/or respiratory symptoms of cough and shortness of breath and are more likely to develop allergies.
Given that there are other means of decontaminating pools such as salt water or ionizers, regulatory bodies should reconsider the appropriateness of chlorine as the standard pool decontaminant.
Dr. O
September 15th, 2009
Everybody Panic!
This is one of those stories that sounds scary as heck, but really isn’t telling us anything of consequence. If you haven’t heard, some researchers cultured material from showerheads and found high levels of the atypical bacteria Mycobacterium avium intracellulare, or MAI, living there. This isn’t very shocking as MAI is a water loving organism.
Anyway the important point here is that MAI is not very pathogenic. Even if you’re exposed to it, the likelihood of it causing clinical disease is exceedingly low. If you have a very weakened immune system, like late stage HIV or post-chemotherapy, you might take notice, but for the vast majority of us this is a non-issue.
Dr. O
