Quote:
Originally Posted by monster
It's several different strains each year, but yes. The thing is, how accurate is the model used to predict the strains? One school of thought in the biz suggests that the currently favoured model is flawed because it predicts speed of spread without taking into acount the increease in intercontinental travel, and as a result is a few years out of date. Right strains, but too late.
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The science behind it is pretty sound:
How effective is the flu vaccine?
How well the flu vaccine works depends on how well the match is between the influenza (flu) vaccine and the types of flu viruses that are circulating that year. Scientists try to predict what strains (types) of flu viruses are most likely to spread and cause illness each year to put into the vaccine. In years when the vaccine strains and the virus strains are well-matched, the vaccine can reduce the chances of getting the flu by 70%-90% in healthy adults. The vaccine may be somewhat less effective in elderly persons and very young children, but vaccination can still prevent serious complications from the flu.
In healthy adults less than 65 years of age, the flu vaccine can also prevent lost work days, and keep you from having to see the doctor or using unnecessary antibiotics.
Is the flu vaccine effective against all types of flu and cold viruses?
The flu vaccine is your best protection against flu viruses. However, the vaccine does not provide protection against non-flu viruses that can cause colds and other respiratory illnesses. It can sometimes be hard to tell the difference between a cold and the flu based on symptoms alone.
The flu vaccine won't protect you from cold or flu viruses that are already in your body when you get a flu vaccine. The flu vaccine takes about two weeks to provide protection from the flu, and it's your best protection to prevent the most common types of flu this season.
Why do I need to get a flu vaccine every year?
Flu viruses change from year to year, which means two things. First, you can get the flu more than once during your lifetime. The immunity (natural protection that develops against a disease after a person has had that disease) that is built up from having the flu caused by one flu virus strain doesn't always provide protection against newer strains of the flu. Second, a vaccine made against flu viruses going around last year may not protect against the newer viruses. That is why the flu vaccine is updated to include current viruses every year.
Another reason to get the flu vaccine every year is that after vaccination, protection from the flu strains in the vaccine decreases over the year.
Because of these reasons, a new flu vaccine is needed each year.
Does the flu vaccine work the same for everyone?
The flu vaccine is the single best way to prevent the flu, and vaccination is the main tool used to protect people from influenza. A number of studies have shown that the flu vaccine works, but how well the vaccine works can change from year to year and vary among different groups of people. The ability of the flu vaccine to protect a person depends on at least two things: 1) the age and health of the person getting the vaccine, and 2) the similarity or "match" between the virus strains in the vaccine and those being spread in the community.
Vaccine effectiveness is not 100%, and some people can still get the flu. For instance, some older people and people with certain chronic illnesses might develop less immunity than healthy young adults after vaccination. However, even for these high-risk individuals, the vaccine still can provide protection against getting severe complications from the flu.
How effective is the flu vaccine in the elderly?
Among elderly persons not living in chronic-care facilities (such as nursing homes) and those persons with long-term (chronic) medical conditions, the flu shot is 30%-70% effective in preventing hospitalization for pneumonia (a lung infection) and influenza. Among elderly nursing home residents, the flu shot is most effective in preventing severe illness, complications that may follow flu (like pneumonia), and deaths related to the flu. In this population, the shot can be 50%-60% effective in preventing hospitalization or pneumonia, and 80% effective in preventing death from the flu.
Because persons aged 65 years and older are at high risk for serious complications from the flu, it also is important that people who live with or care for those at high risk for serious complications get a flu vaccination.
How effective is the flu vaccine in children?
Because children less than 5 years of age are at increased risk of severe flu illnesses, children 6-59 months and the household contacts and caregivers of children 0-59 months are recommended to get the flu vaccine every year. Children less than 6 months of age are most at risk for having complications from flu. However, they are too young to get the flu vaccine. To protect these infants, it is very important that their household members and out-of-home caregivers be vaccinated against the flu.
The flu vaccine can prevent 66% or more influenza infections in young children, with even higher estimates for older children, when the vaccine strains are well-matched to the flu viruses causing illness. Vaccinating close contacts of children can also help decrease children’s risk of getting the flu.
http://www.cdc.gov/flu/about/qa/vaccineeffect.htm