 
The Diseases
Measles
The measles virus is caught through direct contact with an infected
person, or by airborne transmission through coughs or sneezes.
Measles virus is highly infectious, especially before the characteristic
rash appears. The virus belongs to the genus of Morbilliviruses
in the Paramyxoviridae family, which are helical RNA viruses,
including related viruses that cause Newcastle disease and canine
distemper.
Measles symptoms develop 9-11 days after becoming infected and
last up to 14 days. Initial symptoms include irritability, a runny
nose, conjunctivitis (red eyes), a hacking cough and an increasing
fever that comes and goes. The rash starts from day 4, at which
point the fever peaks at around 40.6 °C (105 °F). Flat
red or brown blotches usually start on the forehead and spread
downwards over the face, neck and body. The rash lasts 4-7 days.
There can also be diarrhoea, vomiting and abdominal pain.
One million children die from measles worldwide each year, although the
disease is rare in the UK due to the current vaccination programme.
There were 4168 notified cases of measles in the UK in 1997. However,
only 177 of these were confirmed by laboratory tests. Doctors
may find diagnosis difficult because of the rarity of the disease
in this country; therefore symptoms caused by other viruses may
sometimes be mistaken for measles.
Complications from measles are quite common as the virus can
weaken the body's immune defences. This can allow secondary bacterial
infections to occur in 1 out of 15 notified cases. These include
a severe cough and breathing difficulties (croup), ear infections,
eye infections (conjunctivitis), and viral and bacterial lung
infections such as pneumonia, which affects 1 out of 25 children
with measles.
Severe disease and complications are most likely in
infants under 12 months or those with weakened immune systems.
Inflammation of the brain (acute encephalitis) can occur in 1
out of 1000 cases, and a quarter of those affected are left with
brain damage. SSPE (subacute sclerosing pan-encephalitis) is the
most severe complication of measles, although it is rare (occurring
in 1 out of 100,000 cases). SSPE usually occurs years after the
initial illness and is a slowly progressive brain infection, which
eventually results in death.
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Mumps
Mumps is a highly contagious viral disease that causes painful swelling
of the parotid glands, which are located in the cheeks. Like measles,
mumps is caused by a paramyxovirus, which is spread by droplet
infection (coughs and sneezes). The disease is generally self-limited,
which means that the virus usually clears up completely after
running its course without long-term complications.
The incubation period of the disease is 14-21 days. Children
carrying the virus are infectious from several days before the
swelling appears to several days afterwards. Anyone who is not
vaccinated against mumps is at risk of developing the disease,
though it is most common in children between 5 and 9 years of
age.
Mumps is characterised by painful and swollen glands
in the cheek, neck or under the jaw, affecting one or both sides
of the face. In addition, the child may feel generally unwell
with fever, headache and loss of appetite. Most symptoms are the
result of direct infection of the salivary glands, testes, pancreas,
eyes, ovaries, or kidneys, although there may be central nervous
system involvement as well. Orchitis, or inflammation of the testicles,
affects up to a quarter of adult males with the disease.
Sometimes mumps can lead to inflammation of the central nervous
system, which can result in meningitis (1 out of 20 cases), or
encephalitis (1 out of 1000 cases). Permanent loss of hearing
occurs in 1 out of every 20,000 cases of the disease.
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Rubella
Rubella (German measles) is generally a mild, childhood disease
that causes a rash and fever. The rubella virus is a member of
the Togaviridae family, and has been allocated a genus
of its own- Rubivirus. It has a single-stranded RNA genome,
which is surrounded by an icosahedral-shaped (20-sided) shell.
The virus is spread, like measles, through coughs and sneezes.
Once infected, the rubella virus multiplies in the lining of the
respiratory tract or in lymph nodes before passing into the bloodstream
and spreading throughout the rest of the body.
The period between the time of infection and the appearance of
symptoms is 2-3 weeks. Before the rash appears, the patient can
suffer a light cold and/or swelling in the neck and base of the
skull (due to the enlargement of the lymph nodes). A fine, pink
rash, also called a maculopapular rash, spreads from the forehead
and face downwards, and may last for 1-5 days. Adults often feel
more unwell before the rash appears, and may have pains in the
joints rather like arthritis.
In pregnant women, the virus may infect the placenta via the
bloodstream and replicate there. It can then spread to the foetal
blood supply. Damage to the foetus often occurs because the rubella
virus can stop cell division. This disrupts the development of
many organs including the eye, ear and the brain. Defects occur
in 10-90 % of cases during pregnancy. Major birth defects such
as blindness, deafness, learning difficulties and heart disease
are more likely if infection occurs during the early stages of
pregnancy.
Congenital rubella syndrome (CRS) is the most serious consequence
of rubella. It arises from rubella infection during the first
trimester of pregnancy and can cause abortion, miscarriage, stillbirth
or multiple defects. However, the relationship between foetal
abnormalities and the time of infection is not clear-cut. Once
an infection has been established, it can spread to many organs
and damage may accumulate. Sometimes the onset of CRS symptoms
are delayed until the child is a few months old. Abnormalities
such as hearing loss, mental retardation, physical impairment
and diabetes may not even be displayed until the child has reached
school age.
Other complications associated with rubella include those of the central
nervous system, such as post-infection encephalitis, which occurs
in 1 out of 6000 cases. There is also the rare, late syndrome
of progressive rubella panencephalitis, which is similar to the
condition SSPE that occasionally follows measles.
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The Vaccine
The MMR vaccine contains live measles, mumps and rubella
viruses that have been modified (or attenuated) so that they no
longer cause disease symptoms. The immune system responds to the
vaccine in two ways. First, it makes antibodies against each of
the component viruses in the vaccine, which then destroy them.
Second, special cells called lymphocytes 'remember' certain molecules
on the surface of the three viruses (antigens), so that there
will be a quick immune response if infection by the real viruses
occurs later. Immunity to measles and other antigens in the MMR
vaccine occurs at different times; measles after 6-11 days, rubella
after 10-15 days and mumps after 15-21 days.
The vaccine is given to children at 13 months and
again before they go to school. It was introduced in the UK in
1988.
Preventing outbreaks
The World Health Organisation (WHO) states that at least 95 % of a population
needs to be immunised with a vaccine to effectively prevent outbreaks
of that specific disease. Population protection (also known as
'herd immunity') is necessary to protect children who cannot be
immunised (e.g. those with leukaemia, cancer, AIDS, those on immunosuppressive
treatment or those under one year of age). If measles virus (or
mumps or rubella) does enter the community it is unable to multiply
and so the chances of it being spread to someone who is not immune
is greatly reduced. Women who have not been immunised against
rubella also depend on herd immunity to prevent them from catching
rubella and putting their unborn child at risk. In addition, MMR
vaccine can be used to protect people who have come into contact
with measles during an outbreak of the disease, but it must be
given within three days of exposure.
A single dose of the MMR vaccine protects 90 out of 100 people
against measles and mumps and 97 out of 100 people against rubella.
A second dose of the vaccine increases this level of protection
to over 99 % of the population for all three diseases. Studies
show that when vaccine viruses are combined, the same high levels
of protection are achieved as when the same component vaccine
viruses are given individually.
Possible side effects
The three vaccine viruses in MMR may cause different
side effects at different times. Many are signs that the vaccine
is starting to work and the immune system is responding to immunisation.
Sides affects observed are:
- some children become feverish, develop a measles-like
rash and go off their food 6-10 days after vaccination
- about 3 weeks after their immunisation some children get a
mild form of mumps
- febrile convulsions, or fits associated with a fever, happen
in 1 out in every 1000 children. However, children who catch
measles are 10 times more likely to have a fit than those who
are vaccinated with MMR
- encephalitis (inflammation of the brain) has been reported
(1 case out of a million doses). The risk of children getting
encephalitis after MMR vaccine is no higher than if they had
not had the vaccine. However, the risk of encephalitis is much
higher during a measles infection (1 out of every 5000 cases).
Side effects are much less common after the second (pre-school)
dose. It is worth noting that side effects observed after the
vaccine are the same conditions observed with the natural diseases,
except in the case of the actual disease, the effects are more
severe and more frequently seen.
MMR use worldwide
MMR was introduced in the UK in 1988, but it has been used successfully
in the United States for nearly 30 years and almost 20 years in
Finland. In nearly 30 years, over 500 million doses of MMR have
been given worldwide. Where MMR is available, no countries recommend
giving the vaccines separately.
The exception is Japan, who stopped using MMR in 1993 following
an unacceptable level of adverse reactions. The UK Department
of Health said that the vaccine used in Japan used a strain of
mumps virus that had particular problems. The expected rate of
problems due to immunisation with MMR is 1 out of every 100,000-200,000
children vaccinated. Japan, however, experienced problems with
1 child out of every 900, over 2,000 times higher than normal.
Since 1993, Japan has only offered immunisation against measles
and rubella. They have also had 79 measles deaths between 1992-97,
compared to none in UK.
Some European countries make use of single measles
vaccine in addition to MMR. For example, France recommends that
children are given a single measles vaccine from 9 months of age
if they are in a nursery and there is a risk of a measles outbreak.
These children then receive the required two further MMR vaccinations,
as in the UK.
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The argument for MMR linked to
bowel disease and autism
Dr Andrew Wakefield, of the Royal Free Hospital (RFH)
in London, made the initial observation linking autism to the
MMR vaccine. Dr Wakefield and his colleagues first attempted to
link measles disease and vaccination to bowel diseases, such as
Crohn's disease. The group reported finding measles virus in samples
of bowel disease tissue. Their theory suggested that measles (either
the wild virus or the vaccine virus) could lead to intestinal
inflammation resulting in reduced absorption of essential vitamins
and nutrients in the intestinal tract. This, in turn, could lead
to developmental disorders, such as autism, within 24 hours to
a few weeks of vaccination. The hypothesis was based on a study
of 12 children who had developed behavioural and intestinal problems.
The study was published in The Lancet (1998 Feb; 351:
637-641). The MMR vaccine was considered an obvious source of
the measles virus found in the tissue samples, especially since
the children began to show signs of behavioural problems about
a week after receiving the vaccine.
Drs Wakefield and Montgomery later published an article
in Adverse Drug Reaction and Toxicological Reviews entitled "Measles,
mumps, rubella vaccine: Through a glass darkly" (29 January,
2001), which suggested that the MMR vaccines were licensed prematurely.
This article reviewed the overall situation and earlier work by
Dr Wakefield, but did not provide any new data. In this paper
the authors suggested that there is an increased risk of immune-mediated
disease when the MMR vaccine is administered as one vaccine versus
when the 3 vaccines are administered separately.
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The argument against MMR linked
to bowel disease and autism
Since the initial study by Dr Wakefield at RFH, several
other research groups have attempted to repeat his work. None
of these subsequent studies has been able to detect measles virus
in bowel disease tissue samples.
The reported increase in Crohn's disease in the UK began before
immunisation against measles started. The single vaccine for measles
was introduced in 1968. Use of the triple MMR vaccine began in
1988 and 8 million doses of MR (measles and rubella) were given
in 1994. Studies have shown that the introduction of these vaccines
had no impact on the cases of bowel disease.
The apparent increase in the cases of autism is more recent.
However, immunisation against measles began in 1968 and no change
in the incidence of autism occurred at this time. This would suggest
that only the mumps or rubella components of the MMR vaccine could
be linked to autism, but Dr Wakefield's original study only suggested
a link to measles virus. In addition, a study in 1998 showed that
the national data for Britain indicated a rise in cases of autism
over a decade before the introduction of the MMR vaccine in 1988
and that once it was introduced, there was no change in the number
of cases. This suggests that mumps and rubella can't be linked
to the rise in autism.
Finally, one study showed that there was no evidence for (or
against) an increase in the number of cases of autism; it is just
that there is greater awareness of the disorder.
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Research
In May 2003, US researchers claimed that the MMR jab
was linked to a high number of neurological problems in children.
By analysing data submitted between 1994 and 2000 to the Vaccine
Adverse Events Reporting System, they found that cases of neurological
problems were five times higher after the MMR jab than after the
DTP jab, a combined vaccine for diphtheria, tetanus, and pertussis
(whooping cough). The team concluded that these findings were
not sufficient reason to ban the vaccine, however, they recommended
that it should be redesigned. The UK Health Protection Agency
(HPA) claimed that the research was flawed, as it compared children
from two different age groups. The DTP jab is given at 2, 4 and
6 months, and the MMR is given at 15 to 18 months, which coincides
with the age when neurological disorders begin to be apparent.
HPA believe this in itself could explain why higher numbers of
cases of such disorders are seen in that group of children.
Then, in June 2003, scientists in the US reported
that autism could be caused by mercury. They noticed that the
autistic children in their study had unusually low levels of mercury
in their hair, suggesting that they either accumulate mercury
or cannot expel the heavy metal from their bodies. The group proposed
that a build-up of mercury in brain cells could then trigger autism.
They went on to suggest that a potential source of the heavy metal
could be thimerosal, a mercury-based preservative used in vaccines
(including the DTP jab mentioned in the previous study). The results
could point to a genetic fault that makes the group of children
more susceptible to the effects of mercury. However, the group
did not prove that a low level of mercury in hair is directly
due to its accumulation in the brain. Another suggestion for the
observed low levels of mercury in hair is that the children could
have a problem absorbing any metals from their diet. It is known
that metals such as zinc, copper and iron are essential for normal
brain development. Even if the link is proved, and mercury in
vaccines is confirmed as a cause of autism, this will be good
news for the MMR vaccine, as it contains no mercury.
Finally, in July 2003, US scientists revealed that autistic children
appear to have an abnormal burst of growth in the brain during
their first year of life. The study on children with autism showed
that they tended to be born with small heads, but that their brain
grew rapidly for the first year, and at 12 to 14 months their
heads were larger than 85 % of normal children. The scientists
believed that this unusual rate of growth might damage the baby's
brain and lead to the neurological disorder. As these growth events
occur so early in the life of a child, the findings suggested
that childhood vaccinations (such as the MMR jab) and exposure
to toxins could not play a role in the development of autism.
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Further Information
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