More thoughts on herd immunity
Klock, L.E., et al. "Failure of rubella herd immunity during an epidemic."
New England Journal of Medicine 1973; 288(2):69-72.
Scandals - 07/05/02 Is the theory of "herd immunity" flawed?
Rubella Vaccination - Utilitarianism & Herd Immunity
Excerpted from - Immunization: History, Ethics, Law and Health
By Catherine Diodati
Utilitarianism and herd immunity are central correlative concepts in this
discussion on mass immunization. Utilitarianism refers to the belief that
the greater value (utility/usefulness) of a certain act or rule must be
that which secures the greatest benefit for the greatest number. Herd
Immunity refers to the level of disease resistance of a community or
population. Herd immunity is associated with mass immunization by virtue of
the belief that if high percentages of a population or community are
adequately immunized against certain diseases, virtually all persons will
be protected from disease.
Immunization against rubella presents an interesting example of both the
utilitarian rationale behind mass immunization and of the sometimes
perverse effects of inadequate immunity thresholds and of achieving
targeted immunity thresholds but within the wrong herd population. Mass
rubella immunization, perhaps one of the clearest examples of immunization
for utilitarian purposes, is meant to offer protection, not to the vaccine
recipient but, to fetuses in utero whose susceptible mothers may contact an
infectious carrier. Although contact with the rubella virus does not always
result in congenital rubella syndrome (CRS), the fetus of a non-immune
mother who comes into contact with the virus during the first trimester of
pregnancy may be at risk. For all other populations, "rubella is .a benign
disease that does not justify prevention by vaccination."
To determine the herd immunity threshold for rubella immunization, health
care professionals needed to consider whether it was more effective to
inoculate young children (reducing the risk of infection) or whether to
concentrate inoculations on adolescent girls prior to child bearing age
(decreasing the number of susceptibles).
It appears to be the current practice in Canada, the United States, and the
United Kingdom to immunize children soon after their first birthday thus
reducing the circulation of the wild virus among children. This method for
creating herd immunity has been described in the following way:
Mass childhood rubella immunization programs...designed to produce
"herd immunity" are intended to prevent the spread of rubella to one "herd"
- susceptible women of childbearing age - by creating a high level of
immunity in another "herd" - young population groups. Vaccinating children
en mass against rubella is not justified by any significant health benefits
accrued by the children themselves. Instead, inflicting some measure of
pain and risk of adverse events (e.g. arthritis, autism, etc.) on this one
target population has been justified by the greater utilitarian good
proposed for another population.
It was determined that an 80-85% rubella vaccine threshold coverage is
called for in order to induce herd immunity. Theoretically, unless the
number of immunes reach the targeted goal, either by contracting the
disease naturally or by vaccination, a "proportion of women of reproductive
age [remain] susceptible to the virus and the number of ..cases of
congenital rubella syndrome actually increase[s]." While this may be true
for inadequate immunity rates, it appears that adequate vaccine-induced
herd immunity rates may result in the same perverse consequences.
In the United States, the number of CRS cases reported for 1969, the year
the rubella vaccine was licensed, was 31; that number represents a nearly
three-fold increase in cases reported for each of the three preceding
years. Certainly, as the above theory suggests, the initiation of rubella
immunization, which would not reach herd immunity rates within the first
year, could have resulted in an increase in CRS. Oddly enough, and perhaps
unpredictably, the number of CRS cases did not decline in the following
years despite widespread vaccination. In 1970 and 1971, CRS cases soared to
77 and 68 respectively. In fact, the number of CRS cases remained at very
high levels (30-62 per year) for over a decade before they returned to the
pre-vaccine rates. Quite simply, this method of protecting one "herd" by
creating immunity in another "herd" failed dismally.
Initially, the vaccine had "little or no impact on the number of [rubella]
cases reported" but, even when incidence rates fell into decline during the
1970's there was no concurrent progressive decline in CRS until the early
1980's. What actually happened is that rubella infections became less
common in young children but appeared more frequently in older adolescents
and adults which posed a greater health risk for women of reproductive age.
In 1980 Dr. Cherry, a member of the Advisory Committee on Immunization
Practices, explained that "essentially we have controlled the disease in
persons 14 years or younger but have given it a free hand in those 15 or
older." Contrast this with the fact that naturally occurring rubella
epidemics, in the pre-vaccine era, "produced immunity in about 80% of the
population by 20 years of age" and it becomes evident that, by targeting
the wrong "herd", this immunization strategy produced the opposite results
of those anticipated. Furthermore, from 1970-1988, Britain adopted the
strategy of immunizing only adolescent girls and susceptible women and,
while this strategy did not decrease the number of rubella cases, CRS cases
decreased, albeit slightly. Similarly, from 1979-1982, the US adopted this
same strategy and by 1981 there was a significant decline in CRS cases.
Even though the US returned to the childhood vaccination strategy, both
rubella and CRS cases continued to decline, except for occasional
divergences. It has been suggested, however, that the more recent decline
in CRS may be attributed to other significant "hidden" factors such as a
fall in the fertility rate and the more frequent use of therapeutic
abortions post-exposure. It seems fairly clear that even if herd immunity
thresholds are reached, but they are not reached in the proper populations,
the results are disastrous and contrary to the goals of the herd immunity
If only susceptible women of childbearing age were targeted for
immunization against rubella, it is unlikely that the US would have
experienced such a dramatic increase in CRS cases. Furthermore, this
strategy would have conformed more closely to the utilitarian ethic in a
variety of ways. The vaccine-related costs, pain and adverse events would
have been less burdensome overall. If the naturally acquired disease
continued to produce immunity in 80% of the population, then only a small
percentage would require immunization, fewer individuals would suffer
discomfort, pain and adverse events from the vaccine and the associated
costs. It seems fairly clear that if vaccine-derived herd immunity really
is an utilitarian benefit, then the target populations must be appropriate
or else the result is disastrous.
Challenging "Herd Immunity"
Barbara Sumner-Burstyn: Immunisation choice challenges the herd mentality
The idea of herd immunity - the protection supposedly assured when a large
proportion of a population is vaccinated - is a fundamental element of
immunisation. Concomitant to that is the powerful emotion that your
unimmunised child is a threat to even the immunised children.
But herd immunity is a hotly disputed topic in medical circles.
Many call it one of the great unresearched myths of science.
Formulated in the early 1900s, herd immunity was based on natural, not
Despite reports of epidemics in 100 per cent vaccinated populations and the
fact that vaccine efficacy is more of an educated guess than a known fact,
there really is no proof that herd immunity occurs in vaccinated populations.
The battery of rigorous, long-term, double-blind, placebo-based controlled
trials that are the benchmark in other medical fields are missing from the
development of many modern immunisation serums.
So rather than being blinded by drummed-up hysteria, as one
pro-immunisation article put it, parents, at least those not made braindead
by childbirth, are sifting through all the available information and making
the best decisions they can in a world that oversimplifies complex issues.
This is a world where the parent is ultimately responsible for the
consequences of every decision.
Where, even if they are misled or misinformed, it will still be their fault
when something goes wrong, whichever side of an issue they chose to support.
And perhaps in the end that is the best way. To be the opposite of the
blind-faith parent of previous generations, to be as fully conscious, aware
and responsible as they are capable of every time they make a major decision.
Consequently, despite Dr Tukuitonga's fury over midwives handing out
supposedly wildly inaccurate, anti-immunisation information, he will find
increasingly that conscientious parents will think twice about the
information produced by Governments intent on shutting down all providers
of alternative options.
And even though Drs Tukuitonga and Turner doubt the ability of parents to
wade through dissenting immunisation information, they would be surprised
at just how smart some parents actually are - despite having had children.
"In October, 1972. a seminar on rubella was held at the Department of
Pathology, University Department, Austin Hospital in Melbourne, Australia.
Dr. Beverly Allen, a medical virologist, gave overwhelming evidence against
the effectiveness of the vaccine. So stunned was she with her
investigations that it caused her, like a growing number of scientists, to
question the whole area related to herd immunizations. Dr. Allen described
two trials: the first trial concerned army recruits who were selected
because of their lack of immunity as determined by blood tests. These men
were given Cendevax, an attenuated rubella virus that is supposed to
protect. They were then sent to a camp which usually has an annual epidemic
of rubella. This occurred three to four months after they were vaccinated,
and 80% of the so-called immune recruits became infected with rubella
virus. A further trial shortly after this took place at an institution for
mentally retarded people with similar effects. Additional disturbing
evidence was sent to us by a Melbourne GP who was in the United Kingdom at
the time that Chief Health Officer Sir Henry Yellowlees, had released a
press statement (February 26, 1976) informing doctors that, in spite of
high vaccination figures, there had been no detectable reduction in the
number of babies born with birth defects."--Dr Archie Kalokerinos & Glen
Dettman "Does Rubella Vaccination Protect?," Australian Nurses Journal,
reprinted in The Dangers of Immunisation p54