[Note: AAP = American Academy of Pediatrics; CDC = Centers for Disease Control; VAERS = Vaccine Adverse Event Reporting System]
From the CDC's Vaccine Information Sheet:
HealthCentral provides a selection of pictures of the rash.
From the Nelson Textbook of Pediatrics, 16th edition:
From the AAP Red Book:
The "official" AAP/CDC/AAFP recommended schedule is online. They recommend the first varicella vaccination at 12-18 months. The footnote on varicella is "Varicella vaccine is recommended at any visit, at or after age 12 months for susceptible children (ie, those who lack a reliable history of chickenpox). Susceptible persons aged >= 13 years should receive 2 doses given at least 4 weeks apart"
The AAP policy statement on varicella will give you an overview of the costs and benefits they're balancing with this recommendation. Basically, they say it can avoid an average of 8 days of sickness and lowers future chance of coming down with shingles, and that they didn't see any side-effects in vaccinated children that they didn't see in non-vaccinated children. They note that about 7% of children will develop 2-5 lesions within a month of vaccination. Shingles does occur in people who were vaccinated, but at a lower rate than in those who get the disease.
For more details on costs and benefits, see the 1996 recommendations from ACIP, the Advisory Committee on Immunization Practices. This is the report that evaluated the clinical trials of the vaccine in the US and then recommended universal vaccination.
The bottom line to the pro-vaccination view is that the vaccine is safe, that preventing chickenpox is a good thing for children and their parents, and that the long-term side effects of the vaccine appear to be less severe than the long-term effects of the disease.
The vaccine insert for Merck's VARIVAX is available online.
Various studies while the vaccine was in trials show an 81%-93% reduction in chickenpox cases among the vaccinated children. The cases the did occur were mainly of a mild form, with less than 50 lesions.
Contraindications to vaccination include:
Vaccine recipients should avoid salicylates (aspirin) for six weeks after vaccination to lower the chance of Reye's Syndrome. There were no cases of Reye's Syndrome in the trials, but there have been reports of it in children who get chickenpox naturally and take aspirin.
Adverse reactions reported in clinical trials:
"In addition, the most frequently (>=1%) reported adverse experiences, without regard to causality, are listed in decreasing order of frequency: upper respiratory illness, cough, irritability/nervousness, fatigue, disturbed sleep, diarrhea, loss of appetite, vomiting, otitis, diaper rash/contact rash, headache, teething, malaise, abdominal pain, other rash, nausea, eye complaints, chills, lympadenopathy, myalgia, lower respiratory illness, allergic reactions (including allergic rash, hives), stiff neck, heat rash/prickly heat, arthralgia, eczema/dry skin/dermatitis, constipation, itching.
"Pneumonitis has been reported rarely (<1%) in children vaccinated with VARIVAX; a causal relationship has not been established.
"Febrile seizures have occurred rarely (<0.1%) in children vaccinated with VARIVAX; a causal relationship has not been established."
They also provide a list of additional reactions that have been reported since the vaccine went on the market. There's no frequency information for these:
The National Vaccine Information Center is probably the largest anti-vaccination group around. Their site contains a press release from September 2000 recommending that the vaccine not be given simultaneously with MMR, and saying that their own data on side effects suggests that the VAERS system is not being properly used to track the dangers of vaccination.
VaccineWebsite.com has some information about the vaccine. They concentrate primarily on the data in VAERS, and also suggest a conflict of interest in that some ACIP members own Merck stock. This site does not strike me as a balanced attempt at presenting the medical literature, but it's worth a quick look.
Randall Neustaedter's The Vaccine Guide: Making an Informed Choice (see my review) calls chickenpox "a mild and benign disease of childhood." He's completely against this vaccine: "The foisting of the chickenpox vaccine on the American public qualifies as one of the great marketing scams of the century." He predicts long-term adverse effects including more serious cases of chickenpox in adults as the population becomes increasingly vaccinated. He mentions the long-term risk of shingles without mentioning this as a long-term effect of natural chickenpox infection, and proposes latent virus as a cause of cancer. He fails to mention that the virus remains latent whether you get it naturally or from the vaccine.
A study reported in the March 29, 2001 issue of the New England Journal of Medicine concludes "Varicella vaccine is highly effective as used in clinical practice." They find that the vaccine was 85 percent effective in preventing the disease.
An editorial in the New England Journal of Medicine evaluates the first six years of the varicella vaccine and comes to a positive conclusion:
From a long-term perspective, it is conceivable that varicella-zoster virus will be the first human herpesvirus to be eradicated. Meanwhile, proof of the clinical effectiveness of the varicella vaccine provides further support for the broad implementation of the current recommendations that healthy children and susceptible adults be immunized against varicella-zoster virus.
A November 2001 article in Pediatrics reports on a German study that surveyed the country for all chickenpox complications throughout 1997. They came up with a rate of 8.5 severe complications per 100,000 children. Details of their results:
Results. The response rate to the surveillance questionnaire during the observation period was high: 93.4%. Of the 153 reported cases, 119 met the case definition. There was a seasonal distribution of reported complications with a peak in March. The majority of complications occurred in preschool-age children with a maximum age of 4 years. No gender predominance was found with a distribution of 56 female and 63 male patients. Multiple entries for complications were allowed. The most frequent complications were neurologic, which were reported in 73 children (61.3%); cerebellitis was the leading diagnosis (n = 48), followed by encephalitis (n = 22), meningitis (n = 2), and central facial palsy (n = 1). A total of 46 (38.6%) infectious complications were identified. Superinfections of the skin were present in 31 (26.0%), pyogenic arthritis was present in 5 (4.2%), osteomyelitis was present in 4 (3.3%), necrotizing fasciitis was present in 3 (2.5%), orbital cellulitis was present in 2 (1.6%), and pneumonia was present in 1 (0.8%). Streptococcus pyogenes was the leading cause of bacterial infections (18 cases [15.1%]), with invasive disease in 6 patients (8.4%) and linked to 4 of 8 cases with defect healing. Infectious complications were reported in the majority in younger children up to 4 years of age, whereas neurologic complications occurred more frequently in an older age range. Five children experienced thrombocytopenia or severe anemia. There was no bleeding disorder, no fatality, and no case of Reye syndrome reported during the 1-year observation period. In total, 8 (6.7%) of 119 patients reported having long-term sequelae, 6 attributable to infectious complications and 2 to persistent deficits after neurologic complications.
Also in November 2001, the CDC reports the results of an investigation of administering varicella vaccine at the same time as other vaccines:
This report summarizes an evaluation of these recommendations, which found that a decrease in Var effectiveness occurred when Var was administered <30 days after MMR; therefore, as currently recommended, physicians should administer Var simultaneously with MMR or wait at least 30 days if the vaccines are administered separately.
A CDC investigation reported by Reuters Health in December 2001 looked at a chicken pox outbreak at a day care center in New Hampshire. Among the findings:
The outbreak in 23 children began with a child who had been vaccinated, contradicting the belief that such "breakthrough" cases are not contagious, Dr. Seward noted. The child, a 4-year-old, was confirmed not to have developed varicella infection from the vaccine, but probably developed it after exposure to a sibling with shingles.
Previous findings indicate that the vaccine's effectiveness ranges from 71% to 91%. In the current study, however, the effectiveness that was only about 40%. "Ours is the first study that has shown anything significantly below that level," co-author Dr. B. R. Lee of the CDC told Reuters Health.