Hi, Thanks for posting your query with HCM If your son was given a varicella vacciantion post exposure, there is a high chance that he may be having chicken pox. Without proper examination, it is difficult for me to come to a definite diagnosis. I would recommend you to consult a doctor in your area for proper physical examination and further management. Meanwhile, You could give him anti- pyretic pills or syrup according to his age for fever, so that it doesn t spike much. Vomiting may happen along with fever. If in any case of doubt of an insect bite allergy, look out for symptoms like swellings of lips, eyes, ears, brethlessness and always consult a doctor in these scenarios. I hope this helps Thank you