Vaccine Safety >
Issues of Interest > Multiple Vaccines
The
Safety of Multiple Vaccines
Multiple
Vaccines and the Immune System
Questions
answered on this page:
- How many vaccines does CDC recommend
for children?
- Why does CDC recommend that children
receive so many shots?
- Why are these vaccines given at such a
young age? Wouldn’t it be safer to wait?
- I’ve heard people talk about
"simultaneous" and "combination" vaccines. What
does this mean? Why are vaccines administered this way?
- Is simultaneous vaccination with
multiple vaccines safe? Wouldn’t it be safer to separate combination
vaccines and spread them out, vaccinating against just one disease at
a time?
- Can so many vaccines, given so early
in life, overwhelm a child’s immune system, suppressing it so it
does not function correctly?
- What research has been conducted to
look at the possible link between vaccines and autoimmune diseases?
Related information:
- How many vaccines
does CDC recommend for children?
Currently,
CDC recommends vaccination against 12 vaccine
preventable diseases. Because some of these
vaccines have to be administered more than
once, a child may receive up to 23 shots
by the time he or she is 2 years of age.
Depending on the timing, a child might receive
up to six shots during one visit to the doctor.
- Why does CDC
recommend that children receive so many shots?
CDC recommends
vaccination to protect children against 12
infectious diseases including measles, mumps,
rubella (german measles), varicella (chickenpox),
hepatitis B, diphtheria, tetanus, pertussis
(whooping cough), Haemophilus influenzae
type b (Hib), polio, influenza (flu), and
pneumococcal disease. Vaccines are our best
defense against these diseases which often
result in serious complications such as pneumonia,
meningitis (swelling of the lining of the
brain), liver cancer, bloodstream infections,
and even death.
- Why are these
vaccines given at such a young age? Wouldn’t it be safer to wait?
Children are given vaccines at a young age
because this is when they are most vulnerable to certain diseases.
Newborn babies are immune to some diseases because they have antibodies
given to them from their mothers. However, this immunity only lasts
about a year. Further, most young children do not have maternal immunity
to diphtheria, whooping cough, polio, tetanus, hepatitis B, or Hib. If a
child is not vaccinated and is exposed to a disease germ, the child’s
body may not be strong enough to fight the disease.
An infant’s immune system is more
than ready to respond to the very small number of weakened and killed
antigens in vaccines. Babies have the capacity to respond to foreign
antigens even before they are born. The human immune system has evolved
since organisms began living on Earth and represents a culmination of
the "best" of this experience. Just as babies are born with a
full-length digestive system that simply stretches as the baby grows,
they also are born with a well-developed immune system that can produce
a variety of needed antibodies. However, infants lack the memory cells
trained to defend against specific diseases. Because of this, they are
particularly susceptible to diseases such as diphtheria, whooping cough,
polio, tetanus, hepatitis B, and Hib. This is an important reason why
the recommended childhood vaccination schedule begins so early – to
prevent the diseases that children are susceptible to at such a young
age.
- I’ve heard
people talk about "simultaneous" and "combination"
vaccines. What does this mean? Why are vaccines administered this way?
"Simultaneous vaccination" is
when multiple vaccines are administered during the same doctor’s
visit, usually in separate limbs (e.g., one in each arm). A
"combination vaccine" consists of two or more separate
vaccines that have been combined into a single shot. Combination
vaccines have been in use in the US since the mid-1940's. Examples of
combination vaccines in current use are: DTaP
(diphtheria-tetanus-pertussis), trivalent IPV (three strains of
inactivated polio vaccine), MMR (measles-mumps-rubella), DTaP-Hib, and
Hib-HepB (hepatitis B).
There are two practical factors in
favor of giving a child several vaccinations during the same visit.
First, we want to immunize children as quickly as possible to give them
protection during the vulnerable early months of their lives. Second,
giving several vaccinations at the same time will mean fewer office
visits, which saves parents both time and money and may be less
traumatic for the child.
- Is simultaneous
vaccination with multiple vaccines safe? Wouldn’t it be safer to
separate combination vaccines and spread them out, vaccinating against
just one disease at a time?
The available scientific data show that
simultaneous vaccination with multiple vaccines has no adverse effect on
the normal childhood immune system. A number of studies have been
conducted to examine the effects of giving various combinations of
vaccines simultaneously. These studies have shown that the recommended
vaccines are as effective in combination as they are individually, and
that such combinations carry no greater risk for adverse side effects.
Consequently, both the Advisory Committee on Immunization Practices
(ACIP) and the American Academy of Pediatrics (AAP) recommend
simultaneous administration of all routine childhood vaccines when
appropriate. Research is under way to find methods to combine more
antigens in a single vaccine injection (for example, MMR and
chickenpox). This will provide all the advantages of the individual
vaccines, but will require fewer shots.
Another advantage is that combination
vaccines result in fewer shots and less discomfort for children. In
addition, spreading out the administration of separate vaccines may
leave children unnecessarily vulnerable to disease.
- Can so many
vaccines, given so early in life, overwhelm a child’s immune system,
suppressing it so it does not function correctly?
There is no evidence to suggest that
the recommended childhood vaccines can "overload" the immune
system. In contrast, from the moment babies are born, they are exposed
to numerous bacteria and viruses on a daily basis. Eating food
introduces new bacteria into the body, numerous bacteria live in the
mouth and nose, and an infant places his/her hands or other objects in
his/her mouth hundreds of times every hour, exposing the immune system
to still more antigens. An upper respiratory viral infection exposes a
child to 4 - 10 antigens, and a case of "strep throat" to 25 -
50. According to Adverse Events Associated with Childhood Vaccines,
a 1994 report from the Institute of Medicine, "In the face of these
normal events, it seems unlikely that the number of separate antigens
contained in childhood vaccines . . . would represent an appreciable
added burden on the immune system that would be immunosuppressive."
Vaccines given in the first two years of life have been described as
"a raindrop in the ocean of what infant's immune systems
successfully encounter in their environment every day" (Vaccine
Education Center, Children’s Hospital of Philadelphia, http://www.vaccine.chop.edu/concerns.shtml#question4)
- What research has
been conducted to look at the possible link between vaccines and
autoimmune diseases?
The CDC takes concerns about vaccines
and immune system dysfunction very seriously. Researchers at CDC and
elsewhere have conducted studies to examine the possible link between
vaccines and autoimmune conditions like multiple sclerosis (MS),
diabetes, and asthma. These studies have been reassuring, providing
evidence against a link between vaccines and autoimmune conditions.
However, data has suggested a link between vaccines and other
conditions. For example, recent studies suggest that alopecia (hair
loss) may rarely occur in persons who have received hepatitis B vaccine.
While the mechanisms responsible for
alopecia following vaccination are not certain, it could be
immune-mediated. Thus, CDC continues to conduct research to examine the
effects vaccines may have on the immune system. In addition, CDC and the
National Institutes of Health (NIH) asked the Institute of Medicine
(IOM) to establish an independent expert committee to review hypotheses
about existing immunization safety concerns. On November 12, 2001 the
Immunization Safety Review Committee held an open scientific
meeting to discuss the possible association between multiple
immunizations in newborns and infants and immune system dysfunction.
The IOM report and the news
release are available on the Web at:
References
Tortora GJ, Anagnostakos NP. Principles
of Anatomy and Physiology, 3rd ed. Harper and Row Publishers,
New York, 1981.
Whitney EN, Hamilton EMN, Rolfes SR.
Understanding Nutrition, 5th ed. West Publishing Company, St.
Paul, Minn., 1990.
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