The side effects of the diphtheria vaccine are varied and can occur in both children and adults. Although a majority of the side effects are mild and treatable from home, such as a low-grade fever or diarrhea, immediate medical help should be sought for severe reactions. Difficulty breathing, difficulty swallowing, unconsciousness, convulsions and a high fever are rare but potentially fatal side effects. Disclosing all pre-existing medical conditions and allergies before receiving the vaccination can sometimes prevent serious reactions.
Mild side effects of the diphtheria vaccine are the most common and will develop on the day of the injection. A low-grade fever of 99.5 degrees Fahrenheit (37.5 degrees Celsius) or more can result, which is easily treatable with over-the-counter medication. Diarrhea is another mild side effect that is temporary and treatable from home. Mild redness, tenderness and swelling at the site of the injection are also common.
Children are most likely to develop mild side effects from the diphtheria vaccine. Fussiness and drowsiness can occur for the next few days in infants and young adolescents. Any tenderness from the injection site is likely to increase the child's fussiness. Poor appetite and vomiting are also considered mild side effects and can occur within the next one to three days. A child’s tending physician might recommend over-the-counter medication to alleviate these side effects.
It usually is unnecessary to seek medical attention for mild side effects of the diphtheria vaccine. Moderate side effects should be reported to a physician, however. A low-grade fever, for instance, is treatable from home but a temperature of 103 degrees Fahrenheit (39.4 degrees Celsius) or more can be harmful. Another moderate yet potentially dangerous side effect is a partial seizure that results in staring or jerking.
Severe side effects of the diphtheria vaccine have been known to occur, although these are the most rare. Medical attention should be sought immediately if difficulty breathing, difficulty swallowing, unconsciousness or convulsions occur. A fever of 105 degrees Fahrenheit (40.6 degrees Celsius) or more also requires immediate medical help. All of these side effects of the diphtheria vaccine indicate a serious allergic reaction and most likely will occur within a few hours of receiving the injection.
It is sometimes possible to prevent side effects of the diphtheria vaccine. A pre-existing latex allergy should be disclosed before the injection is given, because some syringes contain a small amount of natural latex rubber. Medical problems such as hemophilia, brain disease, a weakened immune system or a history of seizures also should be disclosed. These pre-existing conditions can increase the chances of developing moderate to severe reactions.