Cedric has a low fever and minor aches. yesterday, he went to the doctor for his booster shot and received the flu shot. which best explains why he has this reaction?

cedric was given an antibiotic.
cedric was too old for the vaccine.
the weakened virus stimulated the immune response and resulted in the minor reaction.
the vaccine contained antibodies that caused cedric to make more antibodies.

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.

italy's population growth rate is almost at zero, the national statistics agency, istat, said on monday, mainly due to a dwindling birth rate.

substitution is the answer in this case