Health Questions & Answers
The Chicken Pox (Varicella) Vaccine

by Gary Emmett, MD

As parents, we often have questions about all kinds of health issues relating to our kids - from illness to prevention to child development. Come ask the experts what you want to know about pediatric health! A selection of answers to your questions will be posted on the site each week.

The question:
Can you tell me about the chicken pox vaccine?

The Pediatrician Answers:
The varicella, or chicken pox, vaccine is a live vaccine given after the first birthday that is effective in preventing chicken pox about 85% of the time and very effective in making it a very mild disease (less than 20 "pox" marks).

Is it safe? This vaccine was used in children and adults who were being treated for leukemia and lymphoma (2 kinds of blood cell cancers) for 15 years until it was released into the general population. There were no significant side effects in this very vulnerable group. About 1 in 20 patients will get a very mild case of chicken pox (again, less than 20 lesions) anywhere from 7 to 21 days after receiving the vaccine, but will not act very ill.

Is it effective? This vaccine, as all vaccines, gets more effective the more people receive it and the less we see the disease. this is call the "herd effective." When in 1995 we had 4 million cases of varicella per year in the United States, it prevent disease completely in about 80% of vaccinated people. This year, 1999, when we will only see 2.5 million cases of varicella, it will be greater than 85% preventative.

Why vaccinate against such a "mild" disease? Because varicella is not a mild disease. In 1995, 50 people in the US died of varicella; 10,000 were hospitalized because of varicella (or its most common secondary infection, which is invasive streptococcal disease). Even not counting the consequenses of rare but very serious consequences such as brain fever (varicella encephalitis), the amount of work missed because of varicella is tremendous (almost a billion dollars per year in 1995). It is a worthwhile shot.

When and to whom is it given? To anyone who is not allergic to eggs, after the first birthday. Up to age 11, one shot and after the 11th birthday, two shots one month apart.

Won't it wear off and cause consequences? It does not seem to wear off very much after more than 20 years experience, but some people will need boosters eventually. More importantly, it has been shown to markedly reduce the incident of another illness caused by the same virus (herpes zoster) called shingles, which are seen in adults primarily and which are very painful.

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About the author: Gary Emmett, MD, is the Clinical Associate Professor of Pediatrics at Thomas Jefferson University in Philadelphia, Pennsylvania. He is Director of General Pediatrics for the Jefferson Health System and Director of the Well Baby Nursery for Thomas Jefferson University Hospital and Methodist Hospital, as well as President of the Philadelphia Pediatric Society. The father of four teens, Dr Emmett still sees at least 100 office visits weekly.