Both the Finnish and the U.S. bird flu vaccines are made by CSL Seqirus but are different vaccines. In the summer, U.S. officials stockpiled 4.8 million doses of the vaccine that officials said was effective against circulating H5N1 strains. In October, the U.S. issued a $72 million grant to three manufacturers to double the nation's stockpile.

Bird flu has led to a wide variety of symptoms during recent outbreaks, including common flu symptoms like cough and vomiting. Many have also had conjunctivitis or pink eye as their only symptom, which experts suspect is from contaminated milk from cows infected by bird flu being splashed onto workers.