Beyond the traditional shots, the squeamish for the first time could try a needle-free injection, or choose the nasal spray or tiny skin-deep needles that have been around for a while. The H3N2 flu subtype always is harsh, especially for older adults, and the vaccine was only 13 percent effective against the mutated version that caused most of last year's illnesses, he said. "[...] the strains in this year's vaccine seem likely to match," Frieden said in an interview Thursday, stressing that CDC is closely monitoring genetic fluctuations to see if that changes. The vaccine protects against three or four different strains, depending on the brand, Schaffner noted, saying that even if one strain mutates, vaccination remains "the best defense against flu." Flu is especially dangerous for people over age 65, young children, pregnant women and people with chronic health conditions such as asthma or heart disease. New CDC data shows vaccination rates last year were highest for children ages 6 months to 23 months — at 75 percent, the only age group to meet public health goals. Most are covered by private and government health insurance, often without a co-pay. Other choices are targeted to different age groups and health conditions and include the "intradermal" or skin-deep shots that use tiny needles; a version for people allergic to the chicken eggs used in brewing most flu vaccine; and a high-dose version for people 65 and older, whose immune systems typically don't respond as robustly to flu vaccine as younger people's.