OOPS: Flu vaccines didn’t work that well in the US, officials find. “This season’s vaccines were around 25% to 30% effective in preventing adults from getting sick enough from the flu that they had to go to a doctor’s office, clinic or hospital, according to a CDC report this week. Children who were vaccinated were about 40% less likely to get treatment at a doctor’s office or hospital. Officials generally are pleased if a flu vaccine is 40% to 60% effective. Judging from past CDC research, this season saw one of the lowest effectiveness rates in the last two decades.”