The Centers for Disease Control and Prevention strongly recommend vaccinating babies against the flu because babies, in particular, are at high risk for severe flu-related complications such as pneumonia and brain inflammation. While the flu vaccine is available in two forms---a nasal spray and a shot---only the shot is Food and Drug Administration (FDA) approved for babies and neither option is approved for babies younger than age six months. Flu shot symptoms are different for babies compared to adults and older children.
Systemic Symptoms
Systemic symptoms of the flu shot include fever, generalized muscle aches, headache and loss of appetite. According to the FDA, about one quarter of vaccinated babies develop fever, defined as oral temperature greater than 100.4 degrees Farenheit or underarm temperature greater than 99.5 degrees Farenheit. In babies, pain symptoms typically manifest as fussiness and irritability and are observed in about half of babies. Approximately 25 percent exhibit poor appetite.
Respiratory Symptoms
Respiratory symptoms of the flu shot in babies include runny nose, cough, sore throat, wheezing and ear aches. The FDA advises that about half of babies demonstrate runny nose. Twenty to 30 percent cough. Wheezing or shortness of breath is observed in fewer than 10 percent of babies and sore throat and ear aches fewer than 3 percent. In almost all cases, respiratory symptoms are mild to moderate and resolve within three to five days.
Injection Site Symptoms
In babies, the flu shot is administered in the large muscle in the front and side of the thigh muscle. According to the FDA, injection site pain and redness develop in about 40 percent of babies. Fifteen to 20 percent of babies exhibit localized swelling. Fewer than one percent of caregivers report severe injection site symptoms and complications like skin infections are rare.
