Shingles and Chickenpox (Varicella-Zoster Virus) - Vaccination

Side Effects of the Varicella (Chickenpox) Vaccine

Discomfort at the Injection Site. About 20% of vaccine recipients have pain, swelling, or redness at the injection site.
Severe Side Effects. Only about 5% of adverse reactions are serious. Between 1995 and 2001, 759 serious adverse effects were reported. Such events included seizures, pneumonia, anaphylactic reaction, encephalitis, Stevens-Johnsons syndrome, neuropathy, herpes zoster, and blood abnormalities.
Risk of Transmission. The vaccine may also produce a mild rash within about a month of the vaccination, which has been known to transmit chickenpox to others. Individuals who have recently been vaccinated should avoid close contact with anyone who might be susceptible to severe complications from chickenpox until the risk for a rash has passed.
Later Infection. Months or even years after the vaccination, some people develop a mild infection termed modified varicella-like syndrome (MVLS). The condition appears to be less contagious and have fewer complications than naturally acquired chickenpox.

Vaccine Long-Term Effectiveness and Possible Need for a Booster

There is currently intense debate over the long-term protection of the vaccine. Such controversy is stimulated by the incidence of breakthrough infections after vaccination. It should be noted, however, that evidence is showing improvements in quality of life and better survival rates since the introduction of the vaccine. Any negative studies to date on long-term effectiveness simply raise the question of the need for booster or higher doses--not the elimination of the vaccine altogether.

Breakthrough Infections and Waning Protection in Vaccinated Children. Studies report that more than 15% of vaccinated children still develop chickenpox (called breakthrough infections). Reasons for this include the following:

Waning Immunity. Studies on children in day care centers report that nearly half of children who had been previously vaccinated develop chickenpox. In one study, children vaccinated within three years had a much lower risk than those whose vaccinations had occurred later. Another study reported a higher risk for breakthrough infections in children who were immunized before 15 months.
Oral Steroids. Children on oral steroids are also at higher risk for a breakthrough infection. (Children taking inhaled steroids, such as for asthma, do not appear to have this risk.)

It should be noted that if vaccinated children develop chickenpox, the cases are nearly always mild and usually less contagious. In such children, the infection appears to be caused by a wild virus, not a reactivation of the vaccine.