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BLFisher Note:
What is not factored into this short-term analysis of varicella vaccine
efficacy is that the vaccine will only provide temporary immunity and children,
who receive it in childhood, will be vulnerable to chicken pox once again as
adults unless booster doses are given. Unlike recovery from the natural
disease, vaccines do not give permanent immunity as has been repeatedly
demonstrated with the failure of the measles and pertussis vaccines to confer
permanent immunity. So, while children in the past experienced chicken pox
disease and remained immune to it for life, which limited susceptibility in the
adult population, mass vaccination with varicella zoster vaccine can only
increase adult susceptibility no matter how high the vaccination rate is in a
population. The result will be increased mortality in the adult population from
chicken pox. Additionally, this live virus vaccine can transmit the vaccine
strain virus to others, further limiting its long term effectiveness as a
medically sound public health intervention enforced by mandatory vaccination
laws.
http://archpedi.ama-assn.org/issues/v155n4/ffull/ped00601.html
To read the full article click on the URL or cut and paste into your browser.
Is It a Good Thing?
James A. Taylor, MD
IN THIS issue of the ARCHIVES, Clements and colleagues1
report on their 5-year cohort study of
varicella among children from 11 day care centers in North Carolina. The
observation period began shortly prior to licensure of the varicella vaccine in
1995; thus, it was possible to compare the rate of disease in the study
population prior to and after initiation of the immunization program, as well
as to monitor the increase in the uptake of the vaccine over time. During the
study, the incidence of varicella was carefully monitored by both a passive reporting
system for parents and day care center personnel and active surveillance
conducted by the research team. Based on the data collected, it was estimated
that varicella vaccine coverage in the day care centers rose from 4% in early
1995 to63% by the end of 1999. As might
be expected, the rate of varicella disease in immunized children was lowranging
from 5.35 cases per 1000 person-months before July 1996, to 1.01 cases per 1000
person-months in late 1999. However,
concurrent with the increased uptake of the vaccine in the day care centers,
the rate of disease in unvaccinated children also fell dramatically. Among
those not vaccinated, the rate of varicella was 16.74 per 1000 person-months
prior to July 1996; by the end of 1999 this rate had decreased to 1.53 per 1000
person-months. The authors conclude that this decrease in varicella in the
unvaccinated children is a demonstration of herd immunity and is a welcome
effect of the vaccine.
[snip]
This is not the case with the varicella vaccine. Although
the incidence of varicella is the highest in young children, the rate of
serious disease is highest in adults. The risk of hospitalization related to
varicella infection is 5 to 10 times higher in adults than in children with the
disease.4 It is therefore conceivable that the herd immunity documented by
Clements et al may have a negative effect on those who have not been
vaccinated. If the incidence of disease in young children is drastically
reduced because of the direct effects of immunization and the resulting herd immunity,
those who are unvaccinated have a reduced chance of acquiring disease during
childhood when the infection is almost always benign. Indeed, this is the “nightmare
scenario” envisioned by those who opposed the recommendation for universal
immunization against varicella.5, 6 It was postulated that while the levels of
varicella vaccination in the population might be just high enough for herd
immunity to occur among young people, they might be just low enough so that a
sizable portion of the adult population would remain susceptible to contracting
the infection at an age when it was more likely to result in significant
complications.
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