medcitynews.com/2016/06/flumist-and-vaccines/
"FluMist is a live attenuated vaccine, meaning it contains a weakened version of the virus itself but does not give the recipient the flu. Instead, it — like other forms of the vaccine — sparks the body’s immune system to create antibodies to the virus. The injectable forms of the vaccine contain killed versions of the virus.
Three months after it made the recommendation, however, the CDC received some troubling data: During the 2013-2014 flu season, the nasal spray showed no measurable effectiveness against the pandemic H1N1 virus in kids aged 2 to 8. That was the predominant type of influenza virus circulating that year.
As a result, the panel in February 2015 did not renew its preference for FluMist for the next flu season, although it was still considered a viable option.
At that meeting, the panel also heard that the spray had performed poorly in the 2014-2015 season.
Because vaccine makers have to guess months ahead of time what the predominant strains of the virus will be, designing the correct combination is always a gamble.
That time, they guessed wrong. More than two-thirds of the H3N2 versions of the virus circulating in the U.S. during the 2014-2015 season were different from the H3N2 versions in both the nasal spray and the injectable vaccines. So all versions of the vaccine — shots and spray — performed poorly.
Now, looking at this winter’s flu season, the CDC says data shows FluMist’s efficacy among children 2-17 was only 3 percent, essentially providing no protective benefit.