 A Guide to Vaccines and
Vaccine Controversies
Stories about vaccines appear in the news at times and they can
make parents wonder whether it is safe to vaccinate their children.
We at Pediatric Affiliates want to make it clear that we feel vaccines are
among the most important things we do to protect your children's health
and that we consider them to be extremely safe. The following
information is a detailed argument about the reasons we feel this
way. It may be a little technical at times but we have tried to make
it comprehensive and complete and hope you find it useful.
Table of Contents:
How
do vaccines work
Vaccines work along a principle that is familiar to people when they think
about chickenpox (now far less common thanks to vaccines). As many
people know, once one has been sick with chickenpox, they are very
unlikely to get sick with it again because their immune system (the cells
that fight infection) has learned to recognize the infection and is ready
to fight it should one get re-exposed. Our immune system recognizes
the infection by learning to recognize small proteins that are
characteristic of that specific infection.
Vaccines work the same way, exposing the recipient to an infection or
parts of an infection so that their immune system will know what to look
for in the future. Nearly all vaccines given in this country are
inactivated infections or just particles from the infection (those
specific small proteins to train our immune system). As a result,
you can not get sick with hepatitis B or influenza from the vaccines,
which are in this category.
The
only live virus vaccines on the regular
vaccination schedule in the U.S. are the MMR (measles, mumps, rubella) and
the chickenpox vaccine. These vaccines are actually live viruses but
in a significantly weakened state. Since they are live viruses it is
possible to get true signs of the infection afterwards (fever, rash) but
because these vaccines are significantly weakened, the reactions are
infrequent and nearly always very mild when they actually do occur.
The trade off is that the MMR and chickenpox vaccines provide immunity
more efficiently than non-live infection vaccines. Children who get
the chickenpox vaccine usually only need one shot to provide lifetime
immunity.
In
contrast, kids need 4 doses of polio vaccine to be protected before they
start school and tetanus boosters are recommended every 10 years (both
polio and tetanus are non-live vaccines). Booster doses basically
help your immune system learn to recognize the infection or refresh the
memory of your immune system which might otherwise forget how to recognize
the infection. Vaccine
schedules are designed to minimize the number of vaccines given while
protecting as many people as possible. For instance, the polio
vaccine is recommended at 2, 4 and 6 months old. Statistically,
perhaps 60% of babies will be immune after getting 1 dose, 90% will be
immune after 2 doses and 98% after 3 doses (not actual figures).
Vaccine
effectiveness
While infectious diseases still afflict us
and our children today, the rates at which people die or have serious
health damage from infections has decreased dramatically in the last
century. The three innovations that changed the world to allow this
are: proper sanitation, antibiotics and vaccines. Vaccines have been so
effective that a disease like smallpox has been eradicated worldwide and
we hope polio is soon to follow. Measles is the third most deadly
infection in the world today (ranking it behind just tuberculosis and
malaria), killing over 500,000 people each year worldwide. But
because of immunizations, measles is now incredibly rare in this
country. And worldwide one could predict that 2 million
deaths from measles are prevented by vaccination each
year! Look at the
following chart to see how cases of infections have changed in the
U.S. for diseases with vaccines*:
|
Disease
|
Average number of infections each year
in the U.S.
|
Percent decrease |
| Smallpox |
48,164 |
0 |
100 % |
| Diphtheria |
175,885 |
2 |
>99 % |
| Pertussis (whooping cough) |
147,271 |
7,580 |
95 % |
| Tetanus |
1,313 |
37 |
97 % |
| Poliomyelitis (paralytic) |
16,316 |
0 |
100 % |
| Measles |
503,282 |
116 |
>99 % |
| Mumps |
152,209 |
266 |
>99 % |
| Rubella |
47, 745 |
23 |
>99 % |
| Haemophilus Influenzae B |
20,000 |
181 |
>99 % |
While you may be impressed by the chart
above, you may think "well, the vaccines have done their part, my child
isn't going to get diptheria today, why should they get the vaccines
now?" There are many answers to that:
-
Many of these diseases still exist and by
not continuing to vaccinate the population they will come back. In
the past 20 years, countries including Japan, the U.K., and Sweden had
periods where less people got the measles and pertussis vaccines and
they saw a resurgence of these infections. In fact, whooping cough
(pertussis) is actually making a comeback in this country (as you can
see in the chart above) and is currently thought to account for a
relatively large percentage of chronic cough infections. This is not
so much a result of kids not getting vaccinated in this country as much
as our relatively recent realization that adults and teens carry and get
sick regularly with this infection and keep it around. While the
pertussis vaccine is part of the tetanus booster children get, it has
only recently been added to teen and adult tetanus boosters in the past
year. Hopefully with this new vaccine, pertussis cases will be cut
to the level of other infections on the chart.
-
Many vaccines protect against infections
more common in other countries (hepatitis B) or in nature (tetanus) that
are likely to stay around in the near future no matter how good a job of
vaccination we do in this country. Some may not happen regularly
in this country but may pop up in outbreaks (hepatitis A).
-
Newer vaccines are fighting against
infections that have been real problems in our lifetime and are changing
the face of illness in kids. Even 15 years ago haemophilus
influenzae B was a common cause of bacterial meningitis is children,
causing hearing loss, brain damage and death. These days that form
of meningitis is rare and it also means that other infections like
pneumonia and even ear infections are less common because that bacteria
has been mostly eliminated. In the past 5 years, new vaccines
against s. pneumonia and n. meningitis promise to do the
same for these bacteria.
Vaccine
safety
 Vaccines can cause
soreness, fussiness and fevers in the first few days after they are
administered. This is likely due to the particles in the vaccine
causing the
immune system reaction that will allow it to produce the cells to
recognize the infection in the future. The live
virus vaccines (MMR and varicella), because they are real although
weak viruses, can cause fever and rash 1-2 weeks after they are given but
should not cause significant infection in people with normal immune
systems. Any medicine or vaccine always carries the risk of an allergic
reaction, but these reactions generally cannot be predicted (except that
people with egg allergies might be sensitive to the flu vaccine).
Beyond those we do not associate other specific reactions with vaccines
(click here
to see the safety handouts on each vaccine). Except for the live
virus vaccines mentioned above, doctors do not think you can get sick with
the infection itself from the vaccine because they are not living
infections. Kids get sick frequently, especially when they go
to day care or school and also after
visiting doctors office waiting rooms. There are many germs in all
these places, and these germs are
likely the source of infections that follow vaccinations (we keep our
offices as clean as possible but doctor's offices are certainly not
sterile).
So why do people and news stories talk about other risks?
Part of the reason vaccine controversies
survive in the news (which likes to create hype) is
because:
-
It is scientifically impossible to
prove one thing absolutely can not cause a second thing.
Extensive studies are done prior to the release of vaccines. All
vaccines given in the population are cataloged and agencies exist for
the reporting of all adverse reactions in the community - not just in
this country but in other countries around the world. Through
these channels the vaccines currently given have not been shown to be
associated with autism, seizures, learning disorders, etc.
However, to say that there is absolutely no relation with these or any
other condition would require studying every person currently alive and
who will be alive in the future. For instance, some kids get
vaccines and get autism but some do not get vaccines and get autism and
most get vaccines and don't get autism but to the best scientific
evidence available (see below) there is no relation between vaccines and
autism.
-
Safety is always a relative term.
Nothing in life has absolutely no risk - whether you are going
skydiving, riding your bicycle, or eating salmon for dinner. In
medicine we often judge safety in terms of these risks weighed against
benefits. Riding your bicycle is fun and good exercise which is
good for you and if done properly (wearing a helmet, reflective light
clothing at night, etc.) probably worth what small risk it
carries. For many skydiving, while probably fun, might be a little
too risky to try. Vaccines, from the best of our scientific study,
do not carry significant risks but do have the real
benefit of protecting our children against real
and deadly infections.
Vaccine
Monitoring
In
addition to the drug companies that produce and test the drugs, drug
safety is monitored in this country by the Centers for Disease Control and
Prevention (CDC) as well as the American Academy of Pediatrics, the Institute of
Medicine and other agencies. Vaccines are also monitored by agencies
in other countries. Reactions to vaccines in the general population
are reported through the Vaccine Adverse Event Reporting System to the CDC.
A few
examples of specific vaccines from the past 20 years are helpful to
illustrate how these reactions really are being monitored:
-
DTP
-
the vaccine most likely to cause fevers
was the DTP (diphtheria, tetanus, pertussis) vaccine. While
having fever some kids had seizures but through further study it was
felt that these kids were likely to have febrile
seizures and seizure problems separate from the vaccine. By
causing fever the DTP vaccine merely unmasked seizure tendencies that
already existed. However, to minimize these fever reactions, a
new acellular pertussis vaccine (the DTaP) vaccine was
developed. The DTaP is the diphtheria, tetanus and pertussis
vaccine we give today and there are much less fever reactions to this
form.
-
Oral polio -
-
Vaccination against polio is unique in
that both a live (but weakened virus) vaccine and an inactivated (dead
virus) vaccine were developed. When polio was a prevalent
problem, the live vaccine worked better than the inactivated
vaccine. This was because the weak but live virus could actually
be spread from person to person so that people in the same house might
actually "catch" the vaccine if they hadn't already gotten it (just
like one may "catch" a stomach virus). However, the downside to
the live vaccine was that in very rare cases it was possible for
someone to get sick with polio from it. But when polio was
common, far more people were protected by the live vaccine than got
sick from the vaccine.
-
However, once polio became rare, the CDC
monitoring reports of reactions to vaccines saw that the risk of
getting sick from the live vaccine was greater than the risk of
getting true polio. Since the inactivated vaccine did not carry
the risk of making people sick while at the same time protecting them
against polio infection, the U.S. switched to give all polio vaccines
in the inactivated form.
-
Rotavirus
-
Rotavirus is a diarrhea illness common
in infants and toddlers that can lead to fevers and dehydration.
This illness causes many hospitalizations in the U.S. While
deaths due to rotavirus occur in underdeveloped countries, deaths from
rotavirus are very rare in this country.
-
A vaccine was developed against
rotavirus in the 1990's to protect against this infection.
However, after it was introduced, case reports indicated a possible
link to intussusception, a surgical condition where a blockage
develops in the intestines that may need surgical correction.
This link was suspected even though it happened in fewer than 0.02% of
infants vaccinated. Since rotavirus is not generally a deadly
infection in this country, it was felt that this possible risk was too
great and this vaccine was withdrawn from the market.
These examples illustrate how vaccines
schedules are modified and improved over time and how reactions to
vaccines are monitored carefully. Decisions about the risks and
benefits of vaccines are always considered and if a vaccine is not
considered to be safe enough, it is removed from the schedule.
What
about other concerns that have been raised in the news?
-
Autism and MMR (measles, mumps, rubella
vaccine) - This is an example of how bad science and associations
can be perpetuated without being substantiated.
-
Autism - autism is a condition where
children have problems with speech and social interactions. The
condition probably is present from infancy but the symptoms usually
become apparent when kids are 12-24 months old and don't talk or
interact like other children. To the best of all current
research, doctors do not know what causes autism - there are
likely both genetic and environmental factors.
-
The controversy about MMR is all
a result of a very small study published in the Lancet journal in 1998
by Wakefield. Basically, Wakefield asked questions of the
parents of 12 children with autism, asking the parents what they
recalled having happened around the time they noticed the onset of
their children's autistic symptoms. As previously mentioned, the
symptoms of autism are usually apparent between 12-24 months of age
(because this is when kids usually start to talk and are more
interactive). So the article noted (not even as its main
conclusion but just as a single point) that 8 of 12 parents recalled
the kids having gotten their 12-month-old MMR shot.
-
The recollection of 8 parents about an
event timed to occur at the same time as one would expect symptoms to
appear is a far cry from evidence of a link but it was enough for the
media to create a controversy. The article itself was withdrawn
from the Lancet because its assertions were felt to suffer from
bias. However, a multitude of studies were done as a result to
see if there was a link. Extensive research on the subject has
continued to find no link between MMR vaccine and autism. A report by the
Institute of Medicine in 2001 said that there was no evidence to
suggest MMR vaccine causes autism or autistic spectrum disorders and
that they could find no biologically plausible method how the vaccine
could cause autism.
-
Autism and Thimerosol
-
Thimerosol is a preservative that had
been used in vaccines and other biological products since the 1930's
to protect the vaccines from contamination. Thimerosol is an
organic compound of ethyl-mercury that was only present in low doses
in vaccines and in studies was shown to be eliminated quickly from the
body (as compared to methyl-mercury, more typically thought of in
mercury poisoning which stays in the body a long time after
exposure). However, since more vaccines are given in recent
years then in the past, there was concern that the total dose of
ethyl-mercury an infant would get through vaccines would be higher
than the FDA guidelines for methyl-mercury. Because of this
calculation (and not because any harm was documented or linked) the
American Academy of Pediatrics in 1999 recommended removal of
thimerosol from vaccines. All formulations of childhood vaccines
for children under 6 years old and under (except for the influenza
vaccine for children over 3 years old) have been thimerosol free since
2002.
-
However, the call to remove thimerosol
from vaccines created controversy. Many studies were done to
evaluate any possible link between thimerosol and autism. A
summary of a few studies as reported in the
Institute of Medicine report as summarized by the New
York Times are as follows:
- "A study by the World Health Organization ... examined the
health records of 109,863 children born in Britain from 1988 to 1997
and found that children who had received the most thimerosal in
vaccines had the lowest incidence of developmental problems like
autism.
- Another study examined the records of 467,450 Danish children
born from 1990 to 1996. It found that after 1992, when the country's
only thimerosal-containing vaccine was replaced by one free of the
preservative, autism rates rose rather than fell.
- In one of the most comprehensive studies, a 2003 report by
C.D.C. scientists examined the medical records of more than 125,000
children born in the United States from 1991 to 1999. It found no
difference in autism rates among children exposed to various amounts
of thimerosal."
In summary, while the prevalence of autism has certainly increased in
recent times, the best evidence from large studies show no connection
between MMR vaccine or thimerosol and autism. Doctors
unfortunately do not know the cause of autism and it is possible that
environmental exposures play a role in this condition. More
research is needed to evaluate the many potentially harmful things are
children are exposed to regularly - from the air we breathe to the food
we eat, etc. To focus excessively on vaccines as a cause, which
are proven to save kids lives from real illness, is likely an
oversimplification.
Other Questions
Q. Is it safe for a young child to receive multiple vaccines at
once?
A. All available research suggests that giving multiple vaccines
simultaneously is effective and safe. Infants and children are
exposed to a multitude of germs daily from food, viruses and
bacteria. Even getting 5 vaccines at once is a small number of
exposures compared to the exposures they contact naturally each day.
Q. Could it be a good idea to separate vaccines onto multiple
days?
A. There is no evidence that it is safer to separate vaccinations
into multiple days. Therefore, the only likely affect of giving
vaccines on extra occasions is that your children are more likely to be
exposed to waiting room germs and be more afraid of doctor's
offices.
Q. Could it be better for my child to get sick with the infections
"naturally"?
A. The chickenpox vaccine is a good case for this
question. Many people think of chickenpox as a relatively benign
illness where you miss school for 2 weeks and are itchy. However,
complications from chickenpox occur regularly, including pneumonia,
meningitis and encephalitis. Complications from the chickenpox are
more likely to occur if one gets sick with chickenpox at an older
age. Even with chickenpox being a live
virus vaccine, the rates of complications are far less with the
vaccine than to get the infection naturally. With chickenpox now
being much less common because of immunization, to not get this vaccine
puts one at risk for getting sick with chickenpox when they are older
and more likely to have complications.
Q. Could it be a good idea to wait until my child is older and
stronger before giving them their vaccines?
A. This question shows how far people's perceptions have
changed because vaccines have been so effective in preventing
infections. The vaccine schedule is created to protect children
from illnesses at the ages they are most vulnerable to the
infection and at an age where the vaccines will be safe and
effective. It is the infections that children need protection
from, not from the vaccines themselves!
We hope this page has been helpful in explaining why we feel vaccines
are safe, effective and important for your child's health. If you
have specific concerns or questions not answered by this page, we welcome
the chance to discuss them with you so your child can be protected.
References
Red Book
2003, Report of the Committee on Infectious Disease, American Academy of
Pediatrics, 26th edition, 2003
Institute of Medicine,
Immunization Safety Review: Vaccines and Autism, 2004
New York
Times, Gardiner Harris and Anahad O'Connor, "On Autism's Cause, It's
Parents vs. Research", 6/25/05
Vaccinecheck.org
(check out Dr. Fineberg's website for further information about vaccines) |
