Immediate medical care may be needed when fever, vomiting, or a seizure occurs along with signs of a serious illness.

Symptoms of serious illness include:

• Severe neck stiffness or pain and fussiness.
• Extreme sleepiness, difficulty waking up, or a lack of alertness.
• A bulging soft spot (fontanel) on a baby's head.
• Rapid, difficult breathing.
• Drooling and not wanting to swallow.
• Severe pain.
• Signs of severe dehydration.
• Blue or purple skin or mucous membranes (cyanosis).
• New skin rash or spontaneous bruising.
• New swelling, pain, redness, or warmth in one or more joints.
• Fever of 105°F (40.6°C) or higher 30 to 60 minutes after giving medication for fever.
• Any signs of a urinary tract infection, such as pain or burning with urination or urinating frequently and in small amounts.