You can tell your child is a toddler by her halting steps or his unsteady gait. Linguists at TheFreeDictionary.com say toddlerhood is between the first and third birthdays. Flu shot aftereffects are uncommon and usually mild in toddlers, according to the U.S. Centers for Disease Control and Prevention, or CDC. The flu, or influenza, vaccine contains only dead or inactivated virus, but rare, serious aftereffects can be reported to the CDC's Vaccine Adverse Effect Reporting System, or VAERS, on-line, by fax or by mail.
Local Swelling
Your toddler may experience redness, soreness and swelling at the injection site for one to two days after the flu shot. MedlinePlus reported in 2010 that seasonal and H1N1, or swine flu, vaccines produced only these mild symptoms in a few toddlers, and no aftereffects in most. This mild inflammatory reaction is not a flu infection. Both the dead and the inactivated influenza viruses used in flu shots are incapable of giving your toddler the flu.
Fever
A low-grade fever lasting for one to two days can develop after your toddler's flu shot, according to MedlinePlus. Toddlers with a low fever are usually irritable and may have reddened or sore eyes, a mild cough, generalized itchiness or an achy feeling. Call your pediatrician if your toddler's fever lasts longer.
Life-Threatening Aftereffects
According to the CDC, life-threatening flu shot aftereffects are exceedingly rare, but when seen, show up within minutes to only a few hours after the shot. Breathing difficulty, sudden lethargy, a rapidly spreading rash or convulsions are among the most obvious signs. If you have a concern based on your toddler's previous reactions to vaccinations, stay in your doctor's office until your doctor says it is safe to go home.
Some parents recall vaccine aftereffect incidents in 1976, when one type of swine flu vaccine was linked to potentially fatal, paralytic Guillain-Barre Syndrome, or GBS. Flu vaccines have not been associated with GBS since then. If a GBS risk occurs with current flu vaccines, only one or two cases in every million vaccinations would be predicted. Failure to vaccinate toddlers carries a much higher risk of illness and death.
Unproven Aftereffects
In July 2010, Mayo Clinic staff pediatricians reported results of their investigations into an alleged connection between flu shots and the development of autism in toddlers. The physicians pointed out that the original report that initiated this controversy was later retracted by its authors. No research has duplicated their disputed results. Mayo Clinic pediatricians assure parents of toddlers that flu shots are safer than catching the flu.
