What is the chickenpox vaccine?

Definition

The chickenpox
vaccine is a live, attenuated vaccine
producing CD4 and CD8 effector and memory T cell antibody immunity to the
varicella zoster virus (VZV), which causes chickenpox.

Pathogenicity and Clinical Significance

Varicella is a highly contagious viral illness caused by VZV, a human
herpesvirus of the Alphaherpesvirinae subfamily.
Transmission is by respiratory droplets or by direct contact with the
virus-containing vesicle fluid. Household transmission rates approach 90
percent.

During the ensuing week, the virus spreads to various parts of the body, including the skin, liver, central nervous system, lymphatic system, and spleen. The majority of affected persons have symptoms that include fever, malaise, and inflamed, pruritic vesicles, which resolve in two to three weeks.

Approximately 1 in 50 persons exhibit complications that include
encephalitis, pneumonia, and hepatitis.
Secondary bacterial skin infections can occur as open skin
lesions provide an entry portal. Varicella virus can be
transmitted through the placenta to the fetus if the disease is acquired by the
pregnant girl or woman during pregnancy. The fetus may be born with congenital
varicella syndrome and demonstrate skin, extremity, ocular, and brain
abnormalities.

Herpesvirus remains dormant in the spinal and cranial sensory ganglia. It
reactivates typically in later life as the person’s antibody level wanes or the
person experiences immune suppression, like that seen in cancer. Reemergence of
the herpesvirus is called shingles and can lead to extremely
painful postherpetic neuralgia, which lasts from weeks to years.

Disease Prevention

The vaccine Varivax was licensed in the United States in 1995. In 1996, the
Advisory Committee on Immunization Practices of the Centers for Disease Control and
Prevention recommended Varivax as part of routine childhood
immunizations. Initially a single dose, a second dose was added in 2006. The
combination vaccine ProQuad, which contains mumps, measles, rubella, and varicella
antigens, was approved in 2005. The vaccine Zostavax has been effective in
boosting cell-mediated immunity (antibody production) and in providing partial
immunity. It is approved for use in persons at age sixty years.

The most common side effects of varicella vaccine include fever, injection-site complaints, and a varicella-like rash. The vaccine is not recommended for persons with hypersensitivity to its ingredients, which include gelatin and neomycin; for persons with immunosuppression or with active tuberculosis; or for women or girls who are pregnant.

Postexposure Vaccine

Post-varicella-exposure vaccination in children has shown some effectiveness in preventing disease if administered within three days of exposure. Protection has not been demonstrated in adolescents and adults.

Impact

Before the development of a chickenpox vaccine, four million people in the United States acquired varicella annually, leading to ten thousand hospitalizations and one hundred deaths. After the development of a vaccine, these numbers were reduced by 85 to 90 percent. The initial vaccine dose reduced varicella infection by 64 percent, and the second dose further reduced infection by 90 percent. Research has shown that the administration of varicella vaccine in childhood reduces the incidence of herpes zoster in adulthood as well.

Bibliography

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Centers for Disease Control and Prevention. “Recommended Immunization Schedules for Persons Aged 0-18 Years—United States, 2008.” Morbidity and Mortality Weekly Report 57 (2008): Q1-Q4. Available at http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5701a8.htm.

_______. “Varicella (Chickenpox) Vaccination.” Available at http://www.cdc.gov/vaccines/vpd-vac/varicella.

Macartney, K., and P. McIntryre. “Vaccines for Post-exposure Prophylaxis Against Varicella (Chickenpox) in Children and Adults.” Cochrane Database of Systematic Reviews (2008): CD001833.Available through EBSCO DynaMed Systematic Literature Surveillance at http://www.ebscohost.com/dynamed.

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Roush, Sandra, et al. “Historical Comparisons of Morbidity and Mortality for Vaccine-Preventable Diseases in the United States.” Journal of the American Medical Association 298, no. 18 (2007): 2155-2163

Smith, Candace, and Ann Arvin. “Varicella in the Fetus and Newborn.” Seminars in Fetal and Neonatal Medicine 14 (2009): 209-217.

Tyring, S. K. “Management of Herpes Zoster and Postherpetic Neuralgia.” Journal of the American Academy of Dermatology 57, no. 6 (December, 2007): S136-S142.

Ward, Mark A. “Varicella.” In Conn’s Current Therapy 2011, edited by Robert E. Rakel, Edward T. Bope, and Rick D. Kellerman. Philadelphia: Saunders/Elsevier, 2010.

Whitley, Richard J. “Varicella-Zoster Virus.” In Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases, edited by Gerald L. Mandell, John F. Bennett, and Raphael Dolin. 7th ed. New York: Churchill Livingstone/Elsevier, 2010.