The following is an educational article written for distribution by the National Immunization Program (NIP) and the Centers for Disease Control (CDC). The article appears in Vidyya as a public service. For more information on information available from NIP, please visit their Web site at www.cdc.gov/nip/publications.
Misconceptions about Vaccination
and how to
respond to them
A great deal of
information about vaccinations is available to parents. This is
good, because parents should have access to any information that
will help them make informed decisions about vaccination.
However, information is sometimes published that is inaccurate or
can be misleading when taken out of context. Following are six
misconceptions that appear in literature about vaccination, along
with explanations of why they are misconceptions.
1. Diseases had already begun to
disappear before vaccines were introduced, because of better
hygiene and sanitation
2. The majority of people who get
disease have been vaccinated
3. There are "hot lots"
of vaccine that have been associated with more adverse events and
deaths than others
4. Vaccines cause many harmful side
effects, illnesses, and even death
5. Vaccine-preventable diseases
have been virtually eliminated from the Unites States
6. Giving a child multiple
vaccinations for different diseases at the same time increases
the risk of harmful side effects and can overload the immune
As a practitioner giving vaccinations, you will encounter
patients who have reservations about getting vaccinations for
themselves or their children. There can be many reasons for fear
of or opposition to vaccination. Some people have religious or
philosophic objections. Some see mandatory vaccination as
interference by the government into what they believe should be a
personal choice. Others are concerned about the safety or
efficacy of vaccines, or may believe that vaccine-preventable
diseases do not pose a serious health risk.
A practitioner has a responsibility to listen to and try to
understand a patient's concerns, fears, and beliefs about
vaccination and to take them into consideration when offering
vaccines. These efforts will not only help to strengthen the bond
of trust between you and the patient but will also help you
decide which, if any, arguments might be most effective in
persuading these patients to accept vaccination.
The purpose of this pamphlet is to address six common
misconceptions about vaccination that are often cited by
concerned parents as reasons to question the wisdom of
vaccinating their children. If we can respond with accurate
rebuttals perhaps we can not only ease their minds on these
specific issues but discourage them from accepting other
anti-vaccine "facts" at face value. Our goal is not to
browbeat parents into vaccinating, but to make sure they have
accurate information with which to make an informed decision.
had already begun
to disappear before vaccines were introduced, because of better
hygiene and sanitation.
Statements like this are very common in anti-vaccine
literature, the intent apparently being to suggest that vaccines
are not needed. Improved socioeconomic conditions have
undoubtedly had an indirect impact on disease. Better nutrition,
not to mention the development of antibiotics and other
treatments, have increased survival rates among the sick; less
crowded living conditions have reduced disease transmission; and
lower birth rates have decreased the number of susceptible
household contacts. But looking at the actual incidence of
disease over the years can leave little doubt of the significant direct
impact vaccines have had, even in modern times. Here, for
example, is a graph showing the reported incidence of measles
from 1920 to the present.
There were periodic peaks and valleys throughout the years, but
the real, permanent drop coincided with the licensure and wide
use of measles vaccine beginning in 1963. Graphs for other
vaccine-preventable diseases show a roughly similar pattern, with
all except hepatitis B* showing a significant drop in
cases corresponding with the advent of vaccine use. Are we
expected to believe that better sanitation caused incidence of
each disease to drop, just at the time a vaccine for that disease
*The incidence rate of
hepatits B has not dropped so dramatically yet because the
infnts we began vaccinating in 1991 will not be at high risk
for the disease unti they are at leasst teenagers. We
therefore expect about a 15 year lag between the start of
universal infant vaccination and a significant drop in
Hib vaccine is another good example, because Hib disease was
prevalent until just a few years ago, when conjugate vaccines
that can be used for infants were finally developed. (The
polysaccharide vaccine previously available could not be used for
infants, in whom most of cases of the disease were occurring.)
Since sanitation is not better now than it was in 1990, it is
hard to attribute the virtual disappearance of Hib disease in
children in recent years (from an estimated 20,000 cases a year
to 1,419 cases in 1993, and dropping) to anything other than the
Varicella can also be used to illustrate the point, since modern
sanitation has obviously not prevented nearly 4 million cases
each year in the United States. If diseases were disappearing, we
should expect varicella to be disappearing along with the rest of
them. But nearly all children in the United States get the
disease today, just as they did 20 years ago or 80 years ago.
Based on experience with the varicella vaccine in studies before
licensure, we can expect the incidence of varicella to drop
significantly now that a vaccine has been licensed for the United
Finally, we can look at the experiences of several developed
countries after they let their immunization levels drop. Three
countries - Great Britain, Sweden, and Japan - cut back the use
of pertussis vaccine because of fear about the vaccine. The
effect was dramatic and immediate. In Great Britain, a drop in
pertussis vaccination in 1974 was followed by an epidemic of more
than 100,000 cases of pertussis and 36 deaths by 1978. In Japan,
around the same time, a drop in vaccination rates from 70% to
20%-40% led to a jump in pertussis from 393 cases and no deaths
in 1974 to 13,000 cases and 41 deaths in 1979. In Sweden, the
annual incidence rate of pertussis per 100,000 children 0-6 years
of age increased from 700 cases in 1981 to 3,200 in 1985. It
seems clear from these experiences that not only would diseases
not be disappearing without vaccines, but if we were to stop
vaccinating, they would come back.
Of more immediate interest is the major epidemic of diphtheria
now occurring in the former Soviet Union, where low primary
immunization rates for children and the lack of booster
vaccinations for adults have resulted in an increase from 839
cases in 1989 to nearly 50,000 cases and 1,700 deaths in 1994.
There have already been at least 20 imported cases in Europe and
two cases in U.S. citizens working in the former Soviet Union.
2. The majority of people who get disease have been vaccinated.
This is another argument frequently found in anti-vaccine
literature - the implication being that this proves vaccines are
not effective. In fact it is true that in an outbreak those who
have been vaccinated often outnumber those who have not - even
with vaccines such as measles, which we know to be about 98%
effective when used as recommended.
This apparent paradox is explained by two factors. First, no
vaccine is 100% effective. To make vaccines safer than the
disease, the bacteria or virus is killed or weakened
(attenuated). For reasons related to the individual, not all
vaccinated persons develop immunity. Most routine childhood
vaccines are effective for 85% to 95% of recipients. Second, in a
country such as the United States the people who have been
vaccinated vastly outnumber those who have not. How these two
factors work together to result in outbreaks in which the
majority of cases have been vaccinated can be more easily
understood by looking at a hypothetical example:
In a high school of 1,000 students, none has ever had measles.
All but 5 of the students have had two doses of measles vaccine,
and so are fully immunized. The entire student body is exposed to
measles, and every susceptible student becomes infected. The 5
unvaccinated students will be infected, of course. But of the 995
who have been vaccinated, we would expect several not to
respond to the vaccine. The efficacy rate for two doses of
measles vaccine can be as high as >99%. In this class, 7
students do not respond, and they, too, become infected.
Therefore 7 of 12, or about 58%, of the cases occur in students
who have been fully vaccinated.
As you can see, this doesn't prove the vaccine didn't work - only
that most of the children in the class had been vaccinated, so
those who were vaccinated and did not respond outnumbered those
who had not been vaccinated. Looking at it another way, 100% of
the children who had not been vaccinated got measles, compared
with less than 1% of those who had been vaccinated. Measles
vaccine protected most of the class; if nobody in the class had
been vaccinated, there would probably have been 1,000 cases of
3. There are "hot lots" of vaccine that have been associated with
more adverse events and deaths than others. Parents should find
the numbers of these lots and not allow their children to receive
vaccines from them.
This misconception got considerable publicity recently when vaccine safety
was the subject of a television news program. First of all, the concept of a
"hot lot" of vaccine as it is used in this context is wrong. It is
based on the presumption that the more reports to VAERS** a vaccine
lot is associated with, the more dangerous the vaccine in that lot; and that by
consulting a list of the number of reports per lot, a parent can identify
vaccine lots to avoid.
This is misleading for two reasons:
A report made to VAERS does not mean that the
vaccine, or other vaccines from the same group or lot caused the event.
VAERS is a national system for reporting health problems that happen around
the same time of the vaccination. Only some of the reported health
conditions are side effects related to vaccines. A certain number of VAERS
reports of serious illnesses or death do occur by chance alone among persons
who have been recently vaccinated.
VAERS reports have many limitations since they
often lack important information, such as laboratory results, used to establish
a true association with the vaccine. For all serious and other clinically
significant events (life-threatening events, hospitalization, permanent
disability, death), follow-up with the health care provider and/or the parent or
vaccinated individual is conducted in an attempt to collect supplemental
information on the reports. Because of the limitations of this type of reporting
system, causality is difficult to determine. Regardless of the cause, VAERS is
interested in hearing about any health concerns that happen around the time of
vaccination. In summary, scientists are not able to identify a problem with a
vaccine lot based on VAERS reports alone without scientific analysis of other
factors and data.
2. Vaccine lots are not the same. The sizes of vaccine lots might vary from
several hundred thousand doses to several million, and some are in distribution
much longer than others. Naturally a larger lot or one that is in distribution
longer will be associated with more adverse events, simply by chance. Also, more
coincidental deaths are associated with vaccines given in infancy than later in
childhood, since the background death rates for children are highest during the
first year of life. So knowing that lot A has been associated with x number of
adverse events while lot B has been associated with y number would not
necessarily say anything about the relative safety of the two lots, even if the
vaccine did cause the events.
Reviewing published lists of "hot lots" will not help parents identify
the best or worst vaccines for their children. If the number and type of VAERS
reports for a particular vaccine lot suggested that it was associated with more
serious adverse events or deaths than are expected by chance, the Food and Drug
Administration (FDA) has the legal authority to immediately recall that lot. To
date, no vaccine lot in the modern era has been found to be unsafe on the basis
of VAERS reports.
All vaccine manufacturing facilities and vaccine products are licensed by the
FDA. In addition, every vaccine lot is safety-tested by the manufacturer. The
results of these tests are reviewed by FDA, who may repeat some of these tests
as an additional protective measure. FDA also inspects vaccine-manufacturing
facilities regularly to ensure adherence to manufacturing procedures and
product-testing regulations, and reviews the weekly VAERS reports for each lot
searching for unusual patterns. FDA would recall a lot of vaccine at the first
sign of problems. There is no benefit to either the FDA or the manufacturer in
allowing unsafe vaccine to remain on the market. The American public would not
tolerate vaccines if they did not have to conform to the most rigorous safety
standards. The mere fact is that a vaccine lot still in distribution says that
the FDA considers it safe.
4. Vaccines cause many harmful side effects, illnesses, and even
death - not to mention possible long-term effects we don't even
Vaccines are actually very safe, despite implications to the
contrary in many anti-vaccine publications (which sometimes
contain the number of reports received by VAERS, and allow the
reader to infer that all of them represent genuine vaccine
side-effects). Most vaccine adverse events are minor and
temporary, such as a sore arm or mild fever. These can often be
controlled by taking acetaminophen before or after vaccination.
More serious adverse events occur rarely (on the order of one per
thousands to one per millions of doses), and some are so rare
that risk cannot be accurately assessed. As for vaccines causing
death, again so few deaths can plausibly be attributed to
vaccines that it is hard to assess the risk statistically. Of all
deaths reported to VAERS between 1990 and 1992, only one is
believed to be even possibly associated with a vaccine. Each
death reported to VAERS is thoroughly examined to ensure that it
is not related to a new vaccine-related problem, but little or no
evidence suggests that vaccines have contributed to any of the
reported deaths. The Institute of Medicine in its 1994 report
states that the risk of death from vaccines is
DTP Vaccine and SIDS
One myth that won't seem to go away is that DTP vaccine
causes sudden infant death syndrome (SIDS). This belief came
about because a moderate proportion of children who die of SIDS
have recently been vaccinated with DTP; and on the surface, this
seems to point toward a causal connection. But this logic is
faulty; you might as well say that eating bread causes car
crashes, since most drivers who crash their cars could probably
be shown to have eaten bread within the past 24 hours.
If you consider that most SIDS deaths occur during the age range
when 3 shots of DTP are given, you would expect DTP shots to
precede a fair number of SIDS deaths simply by chance. In fact,
when a number of well-controlled studies were conducted during
the 1980's, the investigators found, nearly unanimously, that the
number of SIDS deaths temporally associated with DTP vaccination
was within the range expected to occur by chance. In other words,
the SIDS deaths would have occurred even if no vaccinations had
been given. In fact, in several of the studies children who had
recently gotten a DTP shot were less likely to get SIDS.
The Institute of Medicine reported that "all controlled
studies that have compared immunized versus nonimmunized children
have found either no association . . . or a decreased risk . . .
of SIDS among immunized children" and concluded that
"the evidence does not indicate a causal relation between
[DTP] vaccine and SIDS."
But looking at risk alone is not enough - you must always look at
both risks and benefits. Even one serious adverse effect in a
million doses of vaccine cannot be justified if there is no
benefit from the vaccination. If there were no vaccines, there
would be many more cases of disease, and along with them, more
serious side effects and more deaths. For example, according to
an analysis of the benefit and risk of DTP immunization, if we
had no immunization program in the United States, pertussis cases
could increase 71-fold and deaths due to pertussis could increase
4-fold. Comparing the risk from disease with the risk from the
vaccines can give us an idea of the benefits we get from
vaccinating our children.
from Disease vs. Risk from Vaccines
Pneumonia: 1 in 20
Encephalitis: 1 in 2,000
Death: 1 in 3,000
Encephalitis: 1 in 300
Congenital Rubella Syndrome: 1 in 4
(if woman becomes infected
early in pregnancy)
Encephalitis or severe allergic reaction:
1 in 1,000,000
Death: 1 in 20
Death: 3 in 100
Pneumonia: 1 in 8
Encephalitis: 1 in 20
Death: 1 in 200
Continuous crying, then full recovery: 1 in 100
Convulsions or shock, then full recovery:
1 in 1,750
Acute encephalopathy: 0-10.5 in 1,000,000
Death: None proven
The fact is that a child is far
more likely to be seriously injured by one of these diseases than
by any vaccine. While any serious injury or death caused
by vaccines is too many, it is also clear that the benefits of
vaccination greatly outweigh the slight risk, and that many, many
more injuries and deaths would occur without vaccinations. In
fact, to have a medical intervention as effective as vaccination
in preventing disease and not use it would be unconscionable.
Research is underway by the U.S. Public Health Service to better
understand which vaccine adverse events are truly caused by
vaccines and how to reduce even further the already low risk of
serious vaccine-related injury.
diseases have been
virtually eliminated from the United States, so there is no need
for my child to be vaccinated.
It's true that vaccination has enabled us to reduce most
vaccine-preventable diseases to very low levels in the United
States. However, some of them are still quite prevalent - even
epidemic - in other parts of the world. Travelers can unknowingly
bring these diseases into the United States, and if we were not
protected by vaccinations these diseases could quickly spread
throughout the population, causing epidemics here. At the same
time, the relatively few cases we currently have in the U.S.
could very quickly become tens or hundreds of thousands of cases
without the protection we get from vaccines.
We should still be vaccinated, then, for two reasons. The first
is to protect ourselves. Even if we think our chances of getting
any of these diseases are small, the diseases still exist and can
still infect anyone who is not protected. A few years ago in
California a child who had just entered school caught diphtheria
and died. He was the only unvaccinated pupil in his class.
The second reason to get vaccinated is to protect those around
us. There is a small number of people who cannot be vaccinated
(because of severe allergies to vaccine components, for example),
and a small percentage of people don't respond to vaccines. These
people are susceptible to disease, and their only hope of
protection is that people around them are immune and cannot pass
disease along to them. A successful vaccination program, like a
successful society, depends on the cooperation of every
individual to ensure the good of all. We would think it
irresponsible of a driver to ignore all traffic regulations on
the presumption that other drivers will watch out for him or her.
In the same way we shouldn't rely on people around us to stop the
spread of disease; we, too, must do what we can.
a child multiple vaccinations
for different diseases at the same time increases the risk of
harmful side effects and can overload the immune system.
Children are exposed to many foreign antigens every day.
Eating food introduces new bacteria into the body, and numerous
bacteria live in the mouth and nose, 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." And, indeed, 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. In fact,
neither the Advisory Committee on Immunization Practices (ACIP)
nor the American Academy of Pediatrics (AAP) would recommend the
simultaneous administration of any vaccines until such studies
showed the combinations to be both safe and effective. 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 ACIP and AAP recommend simultaneous
administration of all routine childhood vaccines when
appropriate. Research is under way to find ways 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.
There are two practical factors in favor of giving a child
several vaccinations during the same visit. First, we want to
immunize children as early as possible to give them protection
during the vulnerable early months of their lives. This generally
means giving inactivated vaccines beginning at 2 months and live
vaccines at 12 months. The various vaccine doses thus tend to
fall due at the same time. Second, giving several vaccinations at
the same time will mean fewer office visits for vaccinations,
which saves parents both time and money and may be less traumatic
for the child.