According to the Centers for Disease Control and Prevention (CDC), getting an annual seasonal flu vaccination is the first step you should take to reduce your risk of flu. However, according to the U.S. Food and Drug Administration (FDA), the flu shot sometimes causes flu-like symptoms. In almost all cases, these symptoms are mild--they don't interfere with school or work--and short-lived, lasting less than two days.
Fever
The FDA says fever, a temperature greater than 99.9 degrees F, occurs in approximately 1 percent of adults 18 and up. Fever is more common in children: 23 percent of children six months to three years and 16 percent of children three to nine years develop fever within seven days of receiving the shot. However, in order to avoid underreporting, patients who received the flu shot were asked to report all fevers that developed up to five days after the flu shot, even if they probably weren't related to the vaccine.
Pain
"Harrison's Principles of Internal Medicine" says that muscle pain--especially in the legs and lower back--and headache are among the most common symptoms of flu. Similar symptoms sometimes accompany the flu shot, however the prevalence varies by age, with older adults and younger children reporting the fewest pain symptoms. Among adults, according to the FDA, about 15 percent of adults over 65 report headache, muscle pain or both compared to 26 percent for adults between 18 and 65. Among children, about 3 percent of children between six months and three years report pain compared to 14 percent of children between three and nine years.
Nausea, Vomiting and Diarrhea
The prevalence of gastrointestinal symptoms, such as nausea, vomiting and diarrhea seems to decrease with age. According to the FDA, in children between six months and three years, caregivers complained of vomiting, diarrhea or both in up to 15 percent. In children between three and nine years, prevalence was about 8 percent. In adults, 1 percent of those between 18 and 65 and less than 1 percent of those over 65 vomited, although nausea was more common--9 and 3 percent, respectively. In children, researchers measured lack of appetite instead of nausea. Caregivers reported poor appetite in up to 24 percent of younger children and 8 percent of older children.
Ear, Nose and Throat Problems
Temporary ear, nose and throat problems are common in children--but not adults--after the flu shot. The most common problem was runny nose, which occurs in almost 50 percent of children six months to three years and 30 percent children three to nine years. Less common symptoms included cough, sore throat, wheezing/shortness of breath and earache.
References
- CDC: Fighting the flue
- FDA: Influenza virus vaccine
- "Harrison's Principles of Internal Medicine, 17th edition;" A.S. Fauci, E. Braunwald, D.L. Kasper, S.L. Hauser, D.L. Longer, J.L. Jameson and J. Loscalzo (Eds.); 2008
