Chicken pox (varicella) is caused by the DNA varicella zoster virus, which is related to the herpes zoster virus group. Varicella is considered an acute childhood (less than 12 years old) disease, spread through direct human skin-to-skin contact with the skin lesions, through airborne transmission, or through contact with infected conjunctiva. It is highly communicable 1-2 days before, or 4-5 days after, the onset of a rash. This disease presents primarily as a rash, with extremely itchy macules, papules, vesicles, and crusting lesions, that can be on the trunk, the extremities, the scalp, the face, the esophagus, or along the nasopharynx. The prodrome for chicken pox usually includes malaise, itchy skin eruptions, and a fever between 102-103 degrees. The varicella virus can present as an acute condition lasting 2-3 days, as in chicken pox, or through longterm recurrent infections, known as shingles. Shingles typically presents as a “flare up” in a sensory nerve dermatome, manifesting along a specific patch of vesicular eruptions in the skin (CDC, Varicella).
Normally, varicella occurs in temperate regions, in the winter months, typically between March and May. Greater than 95% of individuals in the United States and older have acquired varicella prior to 20 years old. About 2% of adults in the United States are susceptible to varicella, who have not contracted it during childhood. Although a lower percent of adults contract the varicella virus, there is a higher mortality rate (about 55%) associated. Arguments for natural or vaccine-induced immunity against varicella use this point to argue the importance of early immunity from a public health standpoint. Since the introduction of the varicella vaccine in 1995, the epidemiology of varicella, varicella-related deaths, and varicella epidemic outbreaks worldwide has dramatically decreased (Albrecht). Unfortunately, some adverse effects of the vaccine include hepatitis, lymphadenopathy, thrombocytopenia, varicella-like rash at injection site, otitis, dizziness, fatigue, etc. (“Varicella virus vaccine”).
The benefit to having a child contract chicken pox virus naturally is the conference of lifelong natural immunity. Second exposure to the same strain of chicken pox virus rarely manifests as a second outbreak of varicella. Serious complications exist for newborns, children under 1 year old, over 15 years old, and immunocrompromised contracting varicella, such as: dangerously high fever and/or extensive and prolonged illness. One of the most common complications of varicella for healthy children includes secondary streptococcal or staphylococcus infection, which may require hospitalization. Other, more life threatening complications include viral pneumonia, meningitis, or encephalitis following a primary varicella infection. Fortunately, a child’s immune system is equipped to deal with the varicella virus, with hospitalizations incidences occurring for 2-3 persons per 1,000 cases, and death occurring approximately 1 every 100,000 cases for children between 1-14 years old. As mentioned earlier, varicella is a much more serious condition if a child had not been exposed to chicken pox, and contracts the virus as an adult (CDC, Varicella).
The Varivax Vaccine, formulated by Merck, is known as the Chicken Pox vaccine. Varivax is a frozen, dual-staged, high dose, live attenuated Oka varicella virus, designed for individuals 12 months and older in the United States. The Varivax vaccine was attenuated through embryonic lung cell cultures, embryonic guinea pig fibroblasts, and WI-38 human diploid cells, in addition to further attenuations, for a total of 31 passages. The vaccine contains sucrose, processed porcine gelatin, sodium chloride, monosodium L-glutamate, sodium diphopshate, trace amounts of MRC-5 cells and fetal bovine serum, for example. Canada also uses Varivax, same as the United States dosage, or Valrilix, which contains albumin and gelantin, and packaged with diluent (“Varicella virus vaccine”). The Varivax vaccine was originally formulated in Japan in the 1970s, accepted for medical use in Japan in 1988, and first approved and used in the United States in March 1995 (CDC, Varicella).
The Varicella vaccine is a highly effective, subcutaneous, double dose vaccine, conferring 97% immunity for children 12 months to 12 years old, lasting for about 6 years. Risk of transmission of varicella from the vaccine is 2% (very low). For children 13 years and older, typically 78% achieve acceptable antibody titers after a single dose, while 99% immunity occurs after 2 doses of the varicella vaccine. The normal scheduling for the chicken pox vaccine includes the first 0.5 mL subcutaneous dose between 12-15 months old. The second subcutaneous dose of varicella should occur between 4-6 years old, which is also advised to be administered concurrently with the measles-mumps-rubella (MMR) vaccine (CDC, Varicella, “Varicella virus vaccine”). Currently, scientists have improved vaccination design is so that MMRV can be frozen as one vaccine, with a shelf life of 6 months, and promoting ease of administration (Pediatrics Class Notes). Although immunity is common for extended periods of time with the varicella vaccine, if there was a chance occurrence with a breakthrough chicken pox outbreak, the disease would have a much milder effect, with fewer lesions, and less serious complications (CDC, Varicella).
References Albrecht, Mary . “Epidemiology of varicella-zoster virus infection: Chickenpox.” Up to Date . 2011 . Web. 5 Feb 2012.
“CDC – Pinkbook: Varicella Chapter – Epidemiology of Vaccine-Preventable Diseases..” CDC Vaccines and Immunizations. CDC, April 2011. Web. 29 Jan 2012.
Pediatrics 1 Class Notes. Dr. Shiela Kingsbury. Bastyr University, Winter 2012.
“Varicella virus vaccine: Pediatric drug information.” LexiComp . (2012): Web. 5 Feb. 2012. .