Varicella vaccine
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The varicella vaccine protects against the disease commonly known as chickenpox.
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[edit] Dangers of chickenpox
Chickenpox is most often a mild disease, especially for children. Prior to the introduction of vaccine in 1995 in the US (released in 1988 in Japan & Korea), there were around 4,000,000 cases per year in the U.S., mostly children, with typically 100 or fewer deaths. Though mostly children caught it, the majority of deaths (by as much as 80%) were among adults. Additionally, chickenpox involved the hospitalization of about 10,000 people each year.[1]
During 2003 and the first half of 2004, the CDC reported eight deaths from varicella, six of whom were children or adolescents. These deaths and hospitalizations have substantially declined in the U.S. due to vaccination,[2][3] though the rate of shingles infection has increased for the same reason. The vaccine has more recently been determined to be effective at preventing shingles (zoster) in persons 60 years of age and older, if administered regularly.[4]
[edit] Vaccination worldwide
Vaccination is common in the United States, with 41 of the 50 states require immunization for children attending government-run schools. All 50 states offer a medical exemption, and 48 of those states also offering philosophical and/or religious exemptions. The vaccination is not routine in the United Kingdom. Debate continues in the UK on the time when it will be desirable to adopt routine chickenpox vaccination, and in the U.S. opinions that it should be dropped, individually, or along with all immunizations, are also voiced.
Japan was among the first countries to routinely vaccinate for chickenpox. Routine vaccination against varicella zoster virus is also performed in the United States, and the incidence of chickenpox has been dramatically reduced there (from 4 million cases per year in the pre-vaccine era to approximately 400,000 cases per year as of 2005). In Europe most countries do not currently vaccinate against varicella, though the vaccine is gaining wider acceptance. Australia, Canada, and other countries have now adopted recommendations for routine immunization of children and susceptible adults against chickenpox.
Other countries, such as Germany and the United Kingdom, have targeted recommendations for the vaccine, e.g., for susceptible health care workers at risk of varicella exposure. In the UK, varicella antibodies are measured as part of the routine of prenatal care, and by 2005 all National Health Service personnel had determined their immunity and been immunized if they were non-immune and have direct patient contact. Population-based immunization against varicella is not otherwise practiced in the UK. It is feared that there would be a greater number of cases of shingles in adults, until the vaccination was given to the entire population—because adults who have had chickenpox as a child are less likely to have shingles in later life if they have been exposed occasionally to the chickenpox virus (for example by their children). This is because the exposure acts as a booster vaccine.[5][6]
The long-term duration of protection from varicella vaccine is unknown, but there are now persons vaccinated more than thirty years ago with no evidence of waning immunity, while others have become vulnerable in as few as 6 years. Assessments of duration of immunity are complicated in an environment where natural disease is still common, which typically leads to an overestimation of effectiveness, and we are only now entering an era in the U.S. where the long-term efficacy of varicella vaccine can be accurately gauged.[7]
The vaccine is exceedingly safe: approximately 5% of children who receive the vaccine develop a fever or rash, but there have been no deaths yet (as of 1 May 2006) attributable to the vaccine despite more than 40 million doses being administered.[8] Cases of vaccine-related chicken pox have been reported in patients with a weakened immune system,[8][9] but no deaths.
The literature contains several reports of adverse reactions following varicella vaccination,[10][11][12][13][14][15][16][17][18][19][20][21][22] including vaccine-strain zoster in children and adults.[23][24] A mean of 2,350 reports per year are attributed to varicella vaccine based on 20,004 cases reported to the Vaccine Adverse Event Reporting System (VAERS) database from May, 1995 through December, 2003. Minor events are known to be under-reported to VAERS.
[edit] Controversy
Mortality due to primary varicella has declined significantly in countries which make wide use of the varicella vaccine.[2][8] Zoster (shingles) occurs decades after varicella and unsurprisingly zoster incidence has not declined in multiple studies. It is too early to observe the effect on postherpetic neuralgia (PHN).
It has been claimed that shingles may increase after introduction of varicella vaccine.[25][26] There is yet no evidence this has occurred, and it might occur in the absence of immunization due to a general decrease in childhood infection for other reasons.[27]
Additional controversy has arisen because cell lines derived from aborted fetal tissue were used in its development, and thus violates the ethics and beliefs of people who oppose the use of aborted fetal tissue in medical research.CDC
[edit] Duration of immunity
Some vaccinated children have been found to lose their protective antibody in as little as five to eight years; however, according to the World Health Organization: "After observation of study populations for periods of up to 20 years in Japan and 10 years in the United States, more than 90% of immunocompetent persons who were vaccinated as children were still protected from varicella."[1] As time goes on, boosters may be determined to be necessary, and introduced. Persons infected after vaccine experience milder cases of chicken pox.[28]
Catching "wild" chickenpox as a child has been thought to commonly result in lifelong immunity. Indeed, parents have deliberately ensured this in the past with "pox parties" (see below). Historically, exposure of adults to contagious children has boosted their immunity, reducing the risk of shingles.[26] Second episodes of chickenpox have been rare, but occur and probably more frequently in the UK latterly[citation needed] and definitely more frequently in the vaccine group. In one study, 30% of children had lost the antibody after five years, and 8% had already caught wild chickenpox in that five year period.[29]
The CDC and corresponding national organisations are carefully observing the failure rate which may be high compared with other modern vaccines - large outbreaks of chickenpox having occurred at schools which required their children to be vaccinated.[1][2][3][4][5].
[edit] Immunocompromise
The mortality rate in immunocompromised patients with disseminated herpes zoster is 5-15%, with most deaths from pneumonia. Vaccines, unfortunately are less effective among these high-risk patients, as well as being more dangerous because it is an attenuated live virus (see last footnote), but clearly immunization before immunocompromise would be desirable.
[edit] Pox parties
A "pox party" is a party held by parents for the purpose of infecting their children with childhood diseases. Similar ideas have applied to other diseases, e.g. measles, but are now discouraged by doctors and health services due to the risk of serious injury or death (even in children, as described above) from acquiring the disease. The reasoning behind such parties is that guests exposed to the varicella virus will contract the disease and develop strong and persistent immunity at an age before disaster is likely, particularly from chickenpox or rubella.
The first reference to such a practice is the letter of Lady Montagu to Sarah Chiswell describing parties held in Istanbul for the purpose of variolation - an effective technique for gaining immunity to smallpox. Lady Montagu imported the practice to England.
Pox parties have been portrayed in TV cartoons, including South Park ("Chickenpox") and The Simpsons ("Milhouse of Sand and Fog").
An 18th century pox party also features in M.T. Anderson's National Book Award-winning young adult novel, "The Astonishing Life of Octavian Nothing. Volume 1: The Pox Party."
[edit] See also
[edit] References
- ^ a b The Vaccines and other Biologicals department (May 2003). Varicella vaccine. WHO. Retrieved on 2006-08-18. - which includes:
"Varicella vaccines: WHO position paper" (pdf) (1998). Weekly Epidemiological Record 73: 241–248. - ^ a b Seward JF, Watson BM, Peterson CL, et al. (2002). "Varicella disease after introduction of varicella vaccine in the United States, 1995–2000". JAMA 287 (5): 606–11. doi:. PMID 11829699.
- ^ Nguyen HQ, Jumaan AO, Seward JF (2005). "Decline in mortality due to varicella after implementation of varicella vaccination in the United States". N Engl J Med 352: 450–8. doi:. PMID 15689583.
- ^ Oxman MN, Levin MJ, Johnson GR, et al (2005). "A vaccine to prevent herpes zoster and postherpetic neuralgia in older adults". N Engl J Med 352 pages=2271–84. PMID 15930418.
- ^ NHS Direct: Why isn’t the chickenpox vaccine available in the UK?
- ^ UK Health Protection Agency (Prevention section)
- ^ Goldman GS (2005). "Universal varicella vaccination: efficacy trends and effect on herpes zoster". Int J Toxicol 24 (4): 205–213. doi:. PMID 16126614.
- ^ a b c Wise RP, Salive ME, Braun MM, et al. (2000). "Postlicensure safety surveillance for varicella vaccine". JAMA 284 (10): 1271–9. doi:. PMID 10979114.
- ^ Quinlivan MA, Gershon AA, Nichols RA, La Russa P, Steinberg SP, Breuer J (2006). "Vaccine Oka Varicella-zoster virus genotypes are monomorphic in single vesicles and polymorphic in respiratory tract secretions". J Infect Dis 193 (7): 927–30. doi:. PMID 16518753.
- ^ Ravkina LI, Matsevich GR (1970). "Morphological changes in the central nervous system in post-vaccinal encephalomyelitis developing after chickenpox vaccination in children". Zh Nevropatol Psikhiatr Im S S Korsakova 70 (10): 1465–71. PMID 4395233.
- ^ Sunaga Y, Hikima A, Ostuka T, Morikawa A (1995). "Acute cerebellar ataxia with abnormal MRI lesions after varicella vaccination". Pediatr Neurol 13 (4): 340–2. doi:. PMID 8771172.
- ^ Singer S, Johnson CE, Mohr R, Holowecky C (1995). "Urticaria following varicella vaccine associated with gelatin allergy". Vaccine 17 (4): 327–9. doi:. PMID 9987170.
- ^ Gerecitano J, Friedman-Kien A, Chazen GD (1997). "Allergic reaction to varicella vaccine". Ann Intern Med 126 (10): 833–4. PMID 9148672.
- ^ Sakaguchi M, Yamanaka T, Ikeda K, Sano Y, Fujita H, Miura T, Inouye S (1997). "IgE-mediated systemic reactions to gelatin included in the varicella vaccine". J Allergy Clin Immonol 99 (2): 263–4. doi:. PMID 9042057.
- ^ Naruse H, Miwata H, Ozaki T, Asano Y, Namazue J, Yamanishi K (1993). "Varicella infection complicated with meningitis after immunization". Acta Paediatr Jpn 35 (4): 345–7. PMID 8397466.
- ^ Lee SY, Komp DM, Andiman W (1986). "Thrombocytopenic Purpura following varicella-zoster vaccination". Am J Pediatr Hematol Oncol 8 (1): 78–80. PMID 3013041.
- ^ Wrensch M, Weinberg A, Wiencke J, Miike R, Barger G, Kelsey K (2001). "Prevalence of antibodies to four herpesviruses among adults with glioma and controls". Am J Epidem 154 (2): 161–5. doi:. PMID 11447050.
- ^ Naseri A, Good WV, Cunningham ET Jr (2003). "Herpes zoster virus sclerokeratitis and anterior uveitis in a child following varicella vaccination". Am J Ophthalmol 135 (3): 415–7. doi:. PMID 12614776.
- ^ Esmaeli-Gutstein B, Winkelman JZ (1999). "Uveitis associated with varicella virus vaccine". Am J Ophthalmol 127 (6): 733–4. doi:. PMID 10372892.
- ^ Schwab J, Ryan M (2004). "Varicella zoster virus meningitis in a previously immunized child". Pediatrics 114 (2): e273–4. doi:. PMID 15286270.
- ^ Bronstein DE, Cotliar J, Votava-Smith JK, Powell MZ, Miller MJ, Cherry JD (2005). "Recurrent papular urticaria after varicella immunization in a 15-month-old girl". Pediatr Infect Dis J 24 (3): 269–70. doi:. PMID 15750467.
- ^ Binder NR, Holland GN, Hosea S, Silverberg ML (2005). "Herpes zoster ophthalmicus in an otherwise-healthy child". J AAPOS 9 (6): 597–8. PMID 16414532.
- ^ Matsubara K, Nigami H, Harigaya H, Baba K (1995). "Herpes zoster in a normal child after varicella vaccination". Acta Paediatr Jpn 37 (5): 648–50. PMID 8533598.
- ^ Hammerschlag MR, Gershon AA, Steinberg SP, Clarke L, Gelb LD (1989). "Herpes zoster in an adult recipient of live attenuated varicella vaccine". J Infect Dis 160 (3): 535–7. PMID 2547882.
- ^ Yih WK, Brooks DR, Lett SM, Jumaan AO, Zhang Z, Clements KM, Seward JF (2005). "The incidence of varicella and herpes zoster in Massachusetts as measured by the Behavioral Risk Factor Surveillance System (BRFSS) during a period of increasing varicella vaccination coverage, 1998-2003". BMC Public Health 5 (1): 68–68. doi:. PMID 15960856.
- ^ a b Jack (2005). Chickenpox Vaccine Linked with Shingles Epidemic. HerpesDoctor. Retrieved on 2006-08-18.
- ^ Brisson M, Gay NJ, Edmunds WJ, Andrews NJ (2002). "Exposure to varicella boosts immunity to Herpes-zoster: implications for mass vaccination against varicella". Vaccine 20: 2500–7. doi:. PMID 12057605.
- ^ General questions about the disease. Varicella Disease (Chickenpox). CDCP (December 20, 2001). Retrieved on 2006-08-18.
- ^ Pirofski L, Casadevall A (1998). "Use of licensed vaccines for active immunization of the immunocompromised host.". Clin Microbiol Rev 11 (1): 1–26. PMID 9457426.
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