This season’s flu vaccine is identical to last year’s with two type A strains, including the H1N1, and one B strain.
Though unusual, the same predominant flu viruses were circulating around the world both this year and last.
In most years there is “antigenic shift,” or a slight change in the composition of the viruses, necessitating a change in the flu vaccine components.
Each spring three of the predominant circulating flu viruses are chosen to make the flu vaccine.
In this way we build immunity against the anticipated flu virus strains most likely to invade the U.S. in ensuing months.
You still need this year’s vaccine because protection from last year’s flu shot is needed each year for optimal protection.
Children aged 6 months through 8 years during their first year of immunization must receive two doses at least four weeks apart.
The H1N1 flu strain contained in the 2010 vaccine, as well as the 2011 vaccine requires two doses to provide adequate immunity in children 6 months through 8 years. Children 9 years and older require only one dose of vaccine whether they have received the flu vaccine in previous years or not. The only exception is a child who did not receive the flu vaccine last year (2010-11) should receive two doses this year.
The annual flu vaccine should be considered a necessity for all 6 months and older with rare exceptions we will cover in a future article.
The only prevention for the flu is the flu vaccine.