According to the Centers for Disease Control and Prevention (CDC), vaccination is the best way to prevent the contagious chicken pox disease. The vaccine, given to children and adults, may cause reactions in a small number of people.
Short-term swelling and soreness occur at the injection site for about 1 in 5 children and 1 in 3 adolescents and adults.
One in 10 people may have a mild fever in reaction to the vaccine.
About 1 in 25 people react with a mild rash up to a month after vaccination.
The CDC reports that jerking or staring seizure symptoms are infrequent reactions to the vaccine.
Pneumonia has occurred after chicken pox vaccinations. The CDC indicates this is a very rare side effect.
Rare cases of brain reactions and low blood count have been reported but are so infrequent that it cannot be established whether they are a result of vaccine reaction.