The correct answer is The weakened virus stimulated the immune response and resulted in the minor reaction.
The role of vaccination is to activate the immune system against a particular germ which sometimes elicits reactions.
It is a normal behavior of human body to react on administration of a vaccine. Some vaccines have insignificant reactions whereas some causes tenderness, soreness, swelling, flue and mild fever.
Similarly, the reactions which are seen when a flu vaccination is administered includes fever, redness, sneezing, fever and soreness which is the same case with Cedric.
