Friday, September 10, 2010

Does Influenza vaccine help?

Since the winter is coming lets have a quick look into the vaccine and its 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.