I have often heard people reject the vaccine because they once had flulike symptoms after the injection or they had the flu despite the flu.
Facts: 1) The vaccine can not and can not cause flu. Either they were infected before they were immunized or before the immunity started, or the fever and the pain they experienced were side effects of the vaccine, not the flu itself. 2) The vaccine, as it is currently formulated, is far from perfect , In a few years, it was only 20 percent effective to prevent the flu, although it can still reduce the severity of the disease and the likelihood of complications.
The biggest problem with flu vaccines is the need to determine months before the flu season which virus variant is included. The flu virus is a moving target that is heavily exposed to mutations. Even in the production of the vaccine, in which the virus variants are often grown in eggs, they can mutate.
If the variations in the vaccine differ from those that are ultimately responsible for seasonal outbreaks, protection is likely to be greatly reduced, as was the case in the influenza seasons 2004-05 and 2014-15, 19 percent. The vaccine last season was about 36 percent effective.
There is also a difference in the protection afforded by a vaccine given to people of different age groups. For example, the flu vaccine in 2012-2013 had a total impact of 49 percent, but was only 11 percent effective in those aged 65 and over. Older men and women now have a higher-potency vaccine available.
Now there is a common effort to develop a new "universal" flu vaccine that protects against all possible variants and does not require an annual shot. The goal, said Dr. Osterholm, "is a vaccine that can handle many new changes in the virus and that needs to be given only once every five or ten years."
Basic research for the development of such a vaccine could cost a billion dollars a year over the next five to seven years, he estimated. However, the congress provided only $ 100 million for the coming fiscal year.