My 2yo just had his flu vaccine. he squirmed & some of the vaccine ended up on the table. she said "& we only lost a little". is it still effective?

Yes: "A little" means different things to different people. Toddlers getting flu shots for the first time should get 2 shots their first season, which would have been the 2015-16 flu season for a child this age. If none or just one flu shot was given last flu season, such a child should get 2 shots THIS flu season. If this shot was the 3rd flu shot in his life, he's probably as protected as his peers.

Vaccine Spillage: Dosing per mfr.'s recommendation is imperative for all vaccines for optimal response and protection. It is hard to determine the amount lost from your note. It is best to rely on your pediatrician's judgement as to the need to repeat the dosing to assure efficacy of the vaccine. In general extra dosing is not harmful, under dosing may leave the recipient still susceptible to influenza.

Flu vaccine : Children under the age of 35 months are given half of adult dose so that's should be ok . If it's first flu injection then child needs two dosage 1 month apart . If child has had flu injection in past then one dose is enough to protect child .