Final answer:
The correct word to fill in the blank in the given sentence is 'advises', as it implies professional medical guidance suitable for the context.
Step-by-step explanation:
The correct word to complete the sentence 'Every year my doctor __________ me to take flu shot but I refuse so far I have never caught a virus.' is advises. The sentence describes a recommendation rather than an obligation or forceful action, which eliminates 'forces' and 'compels'. 'Encourage' could fit, but 'advise' is more appropriate in a medical context, as it implies professional guidance.