Acute Gastroenteritis: This is a common condition in infants, often caused by viral infections, and can present with vomiting as the sole symptom.

Gastroesophageal Reflux Disease (GERD): Infants with GERD may vomit frequently, especially after feeding, due to the reflux of stomach contents into the esophagus.
Overfeeding or Underfeeding: Incorrect feeding techniques or volumes can lead to vomiting in infants.
Infection: Although the question specifies no other symptoms, it's essential to consider infections such as urinary tract infections or pneumonia, which might not have overt symptoms initially.
Food Allergy or Intolerance: Allergies to proteins in formula or breast milk can cause vomiting in infants.

Pyloric Stenosis: A condition where the pylorus muscle thickens, blocking food from entering the small intestine, leading to projectile vomiting. It's crucial to diagnose early to prevent dehydration and electrolyte imbalances.
Intussusception: A condition where a part of the intestine slides into an adjacent part, potentially cutting off blood supply. It can present with vomiting and is a surgical emergency.
Congenital Heart Disease: Some congenital heart defects can lead to vomiting due to poor feeding or metabolic disturbances.
Metabolic Disorders: Certain metabolic disorders can cause vomiting in infants due to the accumulation of toxic substances.

Congenital Anomalies of the Gastrointestinal Tract: Conditions like esophageal atresia, tracheoesophageal fistula, or duodenal atresia can cause vomiting in infants.
Neonatal Opioid Withdrawal Syndrome: Infants born to mothers who used opioids during pregnancy can experience withdrawal symptoms, including vomiting.
Inborn Errors of Metabolism: Rare genetic disorders affecting metabolism can lead to vomiting among other symptoms.
Central Nervous System Abnormalities: Conditions affecting the brain, such as hydrocephalus or brain tumors, can cause vomiting in infants.