Friday, September 10, 2010

Does Influenza vaccine help?

Since the winter is coming lets have a quick look into the vaccine and its usefulness....as we are going to be asked about this by almost all our patients!
In 2006, the US Advisory Committee on Immunization Practices  published a document where 11 categories of people were listed as being at high risk of complications from influenza. These include healthy adults, 50 to 65 years of age, and healthcare workers.

A recent Cochrane review involving 40 clinical trials which included a total of 70,000 healthy patients < 65 yrs age given either live, inactivated(commonly used in our clinic) or killed vaccines showed the following-
1... In studies where the vaccine strain matched the actual virus (by chance), 1% of pts who had the vaccine developed illness compared to 4% in pts who received placebo.
2... In places where the vaccine strain didnt match the actual disease virus...the corresponding figures were 1% & 2%.
3... Vaccination had a modest effect on time off work( by less than a day) but had no effect on hospital admissions or complication rates. The risk of Gullian Barre that can be attributed to the vaccine is around 1 case per 100,000 vaccinations.

And...what about patients age>65 years? In a study in JAMA 2004, elderly people >65 yrs of age formed the majority of hospital admissions due to influenza. Also ..a study(EPIVAC study) on 1400 community dwelling people age>65 ,with chronic heart disease showed reduction in influenza related mortality with the vaccine.
So in Dec 2009, FDA approved an inactivated vaccine...called Fluzone High Dose, an injectable vaccine that contains 4 times the amount of antigen found in a regular shot. Whether this will translate into a better clinical outcome remains to be seen.
Bottom line - vaccine seems to benefit older patients >65 years and with chronic cardiac or respiratory illness.The use in healthy adults may not have a big benefit.

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