Differential Diagnosis for Fever in a 12-Month-Old After Vaccination

Single Most Likely Diagnosis

• Vaccine-related reaction: The most common cause of fever in a child after vaccination is a reaction to the vaccine itself. Vaccines can cause a mild inflammatory response, leading to fever, which typically resolves on its own within a few days.

Other Likely Diagnoses

• Viral upper respiratory tract infection: Common in children of this age group, especially after exposure to other children, as in a pediatrician's waiting room. Symptoms can include fever, runny nose, and cough.
• Ear infection (Otitis media): A common condition in young children, often following an upper respiratory tract infection. Symptoms can include fever, ear pain, and irritability.
• Gastroenteritis: Viral or bacterial infections that cause diarrhea, vomiting, and fever are common in this age group.

Do Not Miss Diagnoses

• Bacterial meningitis: Although rare, bacterial meningitis is a serious and potentially life-threatening condition that requires immediate medical attention. Symptoms can include fever, irritability, lethargy, and neck stiffness.
• Sepsis: A severe and potentially life-threatening condition caused by a bacterial infection. Symptoms can include fever, lethargy, and poor circulation.
• Febrile seizure: While not an infection itself, febrile seizures can occur in young children with high fevers. Although usually benign, they can be a sign of an underlying serious condition.

Rare Diagnoses

• Kawasaki disease: A rare condition that causes inflammation in the walls of medium-sized arteries throughout the body. Symptoms can include fever, rash, swollen lymph nodes, and red eyes.
• Juvenile idiopathic arthritis: A chronic condition that causes joint inflammation and stiffness. Systemic symptoms can include fever, rash, and swollen lymph nodes.

Treatment and Duration

The treatment and duration of the fever depend on the underlying cause. For vaccine-related reactions and viral infections, treatment is usually supportive, including acetaminophen or ibuprofen for fever reduction, and plenty of fluids. Bacterial infections may require antibiotics. It's essential to consult a healthcare professional for an accurate diagnosis and appropriate treatment.