Influenza vaccine works quite well in young adults. On average, it is 70% to 90% protective in that population. The range is quite wide because each influenza season is different, and some years the virus and the vaccine do not match each other as well as in other years.
In people over about the age of 65, however, the vaccine protection starts to drop. As we get older, our immune system does not respond to new challenges as well as when we were young. It still responds; just not as well. Scientists have studied ways to get the immune system of seniors to respond to vaccines better. We have tried giving multiple doses, adding an immune stimulator called an adjuvant to the vaccine, and increasing the dose of the vaccine. A new high-dose flu vaccine for seniors is available this season, and it works.
The high-dose vaccine contains four times more vaccine per dose than the standard vaccine. It is approved by the FDA for people over 65. It is recommended by the CDC, although the standard vaccine is also approved by the FDA and acceptable for this population.
The high dose vaccine was tested in 2575 seniors in a large trial, and it produced significantly better immunity than the standard dose. Because the high-dose vaccine is new and has obviously not been used against the 2010-11 influenza viruses, we will not know how well it will perform this year until the season is over and we can compare the numbers.
I think it is great that we have a vaccine that is tailored to this specific population rather than giving the same vaccine to everyone. The regular vaccine still works, and I still recommend it, but if you are over 65 and can get the high-dose vaccine, I would get it.