Vaccine Myths

It seems that almost every month newspaper articles and television programs depict the horrors of vaccines. The villains of these stories are greedy vaccine manufacturers, disinterested doctors, and burdensome regulatory agencies. The focus of the stories is that children are hurt unnecessarily by vaccines, and the tone is one of intrigue and cover-up. Perhaps the most dangerous part of these stories (apart from the fact that they may cause many children to miss the vaccines they need) is that the explanations are presented in a manner that seem believable. Below we have listed the most commonly aired stories about vaccines and have tried to separate fact from myth.

MYTH: Vaccines don't work.

Probably the best example of the impact of vaccines is the Hib vaccine, a vaccine that prevents meningitis caused by the bacterium Haemophilus influenza type b (Hib).

The current Hib vaccine was first introduced to this country in 1990. At that time, Hib was the most common cause of bacterial meningitis, accounting for approximately 15,000 cases and 400 to 500 deaths every year. The incidence of cases and deaths per year had been steady for decades. After the current Hib vaccine was introduced, the incidence of Hib meningitis declined to fewer than 50 cases per year! The power of the Hib vaccine is that, because the vaccine was only recently made available, all pediatricians and family practitioners working today saw its impact.

The story of the Hib vaccine is typical of all widely used vaccines. A dramatic reduction in the incidence of diseases such as measles, mumps, German measles, polio, diphtheria, tetanus, and pertussis occurred within several years of the introduction of vaccines against them.

Vaccines not only work, but they work phenomenally well.

MYTH: Vaccines aren't necessary.

In some ways, we are victims of our own success. Most young parents today have never seen a case of measles, mumps, German measles, polio, diphtheria, tetanus, or whooping cough. Some of these parents question the continued need for vaccines.

Vaccines should be given for one of three reasons:

• Some diseases are so prevalent in this country that a decision not to give a vaccine is a decision to get that disease (for example, chickenpox).
• Some diseases continue to smolder just below the surface. These diseases continue to occur, but at fairly low levels (for example, measles, mumps, German measles, and pertussis). If immunization rates drop, outbreaks of these diseases will again occur and children will die from our lack of vigilance. This is exactly what happened in the late 1980s when immunization rates against measles dropped. The result was 100,000 cases of measles and more than 100 deaths! Last year, due to an increase in measles immunization rates, there were only 89 cases of measles and no deaths.
• Some diseases have been virtually eliminated from this country (such as polio and diphtheria). However, these diseases continue to cause outbreaks in other areas of the world. Given the high rate of international travel, these diseases could be easily imported by travelers or immigrants.

MYTH: Vaccines are not safe.

Despite what is often stated in the media, all recommended vaccines are extraordinarily safe. Side effects from vaccines are usually limited to pain and tenderness where the shot was given or low-grade fever. However, side effects from three vaccines are more worrisome: the "old" pertussis vaccine, the oral polio vaccine (OPV), and the rotavirus vaccine.

The "old" pertussis vaccine (in the preparation called DTP) was a rare cause of persistent crying, seizures, and high fever. Although children were not permanently damaged by the vaccine, it was still very difficult for parents to watch their children suffer these side effects. Fortunately, the new pertussis vaccine (DTaP) is purer than the old vaccine and will likely reduce or eliminate these rare side effects.

Another vaccine that is problematic is OPV. OPV itself can be a rare cause of complete and lifelong paralysis, usually after the first dose. Because poliovirus was eliminated from the Western Hemisphere in 1991, the only children who now get polio in this country are those who received OPV. To eliminate this problem, the Centers for Disease Control and Prevention (CDC) and the American Academy of Pediatrics (AAP) recently recommended that OPV no longer be used in this country. Instead, four doses of inactivated polio vaccine (IPV) are now routinely recommended for all children. IPV does not cause paralysis.

The rotavirus vaccine, first available in September 1998, was voluntarily withdrawn by the manufacturer pending further studies to determine whether it caused a rare intestinal disorder termed intussusception. These studies should be completed by October 1999. Intussusception is caused when the intestine folds in on itself and results in intestinal blockage, pain, blood in the stools, and cramping. Intussusception may occur in as many as 1 in 1,000 recipients of the rotavirus vaccine. (Intussusception occurs at a rate of about 1 in 2,000 in the general population.) If the current rotavirus vaccine is no longer available, this will mean that, until a safer rotavirus vaccine is available, children will again be forced to suffer the disease caused by rotavirus. This disease causes 1 in 50 children to be hospitalized and as many as 50 children to die every year in the United States.

MYTH: Infants are too young to get vaccinated.

Children are immunized in the first few months of life because a number of vaccine-preventable diseases infect them when they are very young.

For example:

• Pertussis infects about 7,000 children, causing six deaths every year in the United States. Almost all of the cases are in children less than 1 year of age.
• Children under 2 years old are 500 times more likely to catch Hib meningitis if someone with a Hib infection is living in the home.
• About 90 percent of newborns whose mothers are infected with hepatitis B will contract hepatitis and go on to develop chronic liver disease, cirrhosis, and possibly liver cancer.

For these reasons, it is very important for infants to be fully immunized against certain diseases by the time they are 6 months old.

Fortunately, young infants are surprisingly good at building immunity to viruses and bacteria. About 95 percent of children given DTaP, Hib, and hepatitis B virus vaccines will be fully protected by 6 months of age.

MYTH: It's better to be naturally infected than immunized.

It is true that "natural" infection almost always causes better immunity than vaccination (only the Hib and tetanus vaccines are better at inducing immunity than natural infection). Whereas natural infection causes immunity after just one infection, vaccines usually create immunity only after several doses are given over a number of years. For example, DTaP, hepatitis B, and polio are each given at least three times.

However, the difference between vaccination and natural infection is the price paid for immunity. The price paid for vaccination is the inconvenience of several shots and the occasional sore arm. The price paid for a single natural infection is usually considerably greater: paralysis from natural polio infection, mental retardation from natural Hib infection, liver failure from natural hepatitis B virus infection, deafness from natural mumps infection, or pneumonia from natural varicella infection are high prices to pay for immunity.

MYTH: Vaccines weaken the immune system.

Natural infection with certain viruses can indeed weaken the immune system. This means that when children are infected with one virus, they can't fight off other viruses or bacteria as easily. This happens most notably during natural infection with either chickenpox or measles. Children infected with chickenpox are susceptible to infection with certain bacterial infections (like "flesh-eating" bacteria). And children infected with measles are more susceptible to bacterial infections of the bloodstream (sepsis).

But vaccines are different. The viruses in the measles and chickenpox vaccines (the so-called vaccine viruses) are very different from those that cause measles and chickenpox infections (the "wild-type" viruses). The vaccine viruses are themselves so disabled that they cannot weaken the immune system.

MYTH: Vaccines use up the immune system.

Is it possible that all the vaccines given to children in the first few months of life use up the immune system? Certainly children build immunity to only a limited number of microorganisms (viruses, bacteria, fungi, or parasites). The question is, how many?

Probably the most sensible approach to answering this question was that formulated by Drs. Mel Cohn and Rodney Langman, immunologists working at the Developmental Biology Laboratory at The Salk Institute in San Diego. They theorized that the number or microorganisms to which a body can respond depends on the number of cells in blood that can make antibodies sufficient to recognize all the relevant parts of the microorganism.

Using their theory, it stood to reason that the number of microorganisms to which one responds depends on one's size. Cohn and Langman estimated that elephants can produce immunity to about 100 times more organisms than humans, and that humans can build immunity to at least 100 times more organisms than hummingbirds. Although this would mean that adult humans could make antibodies to more organisms than infants, the scientists estimated that even young infants could respond to about 100,000 different organisms.

Therefore, the 10 vaccines required for all children will use up only about 0.01 percent of the immunity that is available.

MYTH: Some vaccines contain other infectious agents that may damage my child.

All currently recommended vaccines are tested by pharmaceutical companies under the strict supervision of the Food and Drug Administration (FDA). Vaccines are tested for the presence of known viruses, bacteria, fungi, or parasites different from those contained in the vaccine.

When you consider that the 3.5 to 4 million children born every year in the United States receive 10 different vaccines by the time they are 6 years old, and that some of these vaccines have been in existence for over 50 years, the record of vaccine safety in this country is remarkable.

MYTH: Vaccines cause autism.

In 1998, a study published in the English journal Lancet reported that autism might be caused by the combination measles, mumps, and rubella (MMR) vaccine. The report claimed that children given this vaccine developed inflammation of their intestines that preceded the development of autism. Based on this study, The Medical Research Council of Britain set up a panel to investigate a possible link between MMR vaccine and autism.

A subsequent study showed that there was no association between vaccines and autism. The two studies were very different in the quality and analysis of data. The second study (disproving an association between vaccine and autism) evaluated 500 children; the first study evaluated only 12. The second study included statistical methods adequate to determine whether MMR cause autism; the first study did not. The second study carefully evaluated the effect of MMR when first introduced into Britain on the incidence of autism; the first study did not. So, in short, the second study was much better than the first study and enabled one to conclude that MMR and autism were not linked.

So how are parents supposed to distinguish between scientific studies? Some parents saw a report in the media that the MMR vaccine might be linked to autism, and then they saw a study that disproved this association. (The second study, however, received far less media coverage than the first.) For parents and the media the score was one study in favor of an association and one study against an association.

Unfortunately, few parents or journalists have the medical, epidemiologic, or statistical background to distinguish adequately between these studies. And, quite frankly, many doctors don't have the time to read and evaluate the statistics of all published studies. Doctors rely on associations composed of experts in various fields to determine whether to use a particular medicine or vaccine. Associations like the American Academy of Pediatrics, the Centers for Disease Control and Prevention, the American Association of Family Physicians, the Advisory Committee on Immunization Practices to the CDC, and many disease-centered societies (such as the Multiple Sclerosis Society) are composed of scientists, clinicians, epidemiologists, parents, and statisticians who contribute their time and efforts to these organizations. Experts donate their time for one simple reason: They care deeply about the health and well-being of children.

Parents should do what doctors do: Heed the advice of these experts. Although this may sound like an anti-intellectual recommendation, it remains a reasonable recommendation. The fields of immunology, pathogenesis, statistics, virology, and vaccinology are complex. It takes decades to develop an expertise in each one. Although it is obviously valuable for parents to understand as much as they can about vaccines (which is why we wrote this book), it is simply not possible to gain an adequate expertise in these fields by reading. We are invariably best served by trusting experts.

Experts decided to temporarily suspend administration of the rotavirus vaccine. Experts decided to suspend the use of the polio vaccine manufactured by Cutter Laboratories. And experts have warned for decades about the side effects of some vaccines (for example, that the influenza vaccine should not be used by people allergic to eggs). If well-controlled, adequately analyzed studies clearly showed that MMR caused autism, experts in the field would be quick to ask for the vaccine to be withdrawn.

MYTH: A preservative contained in many vaccines harms children.

In 1999, a study revealed that the preservative thimerosal, a mercury-containing compound present in many vaccines, caused several infants to have levels of mercury in their blood that exceeded guidelines recommended by the Environmental Protection Agency (EPA). Exposure to high levels of mercury (especially in the developing fetus) is associated with neurologic disturbances. When this study was first described, physicians, scientists, and public health officials were undecided about what to do. Several facts accounted for their confusion.

• Although levels of mercury exceeded EPA guidelines, they did not exceed guidelines recommended by the Food and Drug Administration (FDA), the agency that is responsible for the safety of drugs and biologics (such as vaccines). The EPA, in contrast, is responsible for environmental agents.
• Levels of mercury calculated by the EPA were derived from studies of adults in Iraq, the Faroe Islands, and the Seychelles who had chronically ingested fish containing high levels of mercury. These studies were then used to extrapolate levels of safety to young children injected with trace levels of mercury contained in vaccines. Many scientists and toxicologists felt that this was an unreason- able extrapolation.
• Vaccines containing thimerosal have been used since the 1930s and no child has ever been shown to be harmed by the trace amounts of thimerosal contained in vaccines. Preservatives are used in vaccines to reduce the risk that the vaccine would be contaminated by bacteria once the vial is opened.
• Thimerosal contains ethyl mercury, not the methyl mercury that was contained in fish.
• Mercury is commonly found in the environment in the United States. Mercury is contained in trace quantities in water, dental amalgams, cosmetics, and topical antiseptics (such as Mercurochrome and Merthiolate). We are all, therefore, routinely exposed to trace quantities of mercury in the environment.
• Mercury is eliminated from the body within 2 months, an interval commonly used to administer vaccines.

But the CDC and AAP feared that vaccines containing thimerosal would be "perceived" as unsafe. So, they recommended that thimerosal be removed from vaccines as quickly and efficiently as possible. The removal of thimerosal from vaccines eliminates an agent that, when encountered in high quantities, can cause neurologic damage. However, as was stated by both the CDC and AAP when they issued their joint statement, "there are no data or evidence of any harm caused by the level of exposure that some children may have encountered in following the existing vaccine schedule." Although the removal of thimerosal from vaccines has not caused them to be safer, it has allowed them to be perceived as safer.

MYTH: The hepatitis B vaccine causes sudden infant death syndrome (SIDS).

The ABC program 20/20 aired a story claiming that the hepatitis B vaccine caused SIDS. They showed the picture of a 1-month-old girl who had died of SIDS only 16 hours after receiving her second dose of hepatitis B vaccine. To the reporters of this story, this proved that the hepatitis B vaccine caused SIDS. Although anecdotes can be quite powerful, they can also be misleading.

Every year in the United States, about 5,000 infants die of SIDS. The hepatitis B vaccine is now routinely recommended for infants as a series of three shots. Therefore, some infants who get the hepatitis B vaccine will invariably die from SIDS-and some will die from SIDS soon after the vaccine was given. But does this mean that children who get the vaccine are more likely to die from SIDS than children who don't get the vaccine.

To really understand if a vaccine causes problems you need more information. You need to know the incidence of SIDS in those who got the vaccine and the incidence of SIDS in those who didn't get the vaccine. Anecdotes do not provide this information. When the incidence of SIDS is examined in immunized and unimmunized infants, there is no evidence that the hepatitis B vaccine causes SIDS.

Indeed, SIDS had been described as a problem in the United States well before the hepatitis B vaccine was made available.

The hepatitis B vaccine, like all vaccines, is designed to prevent only one disease. Children who get the hepatitis B vaccine will be prevented from hepatitis B virus infections, but they will not be prevented from SIDS or any number of other illnesses that occur in the first year of life.

MYTH: Pharmaceutical companies occasionally manufacture lots of vaccines that cause high rates of adverse events ("hot lots").

Individual lots of vaccines that have unusually high rates of side effects have never been identified in this country. Therefore, specific lots of vaccines have never been withdrawn from use as a "hot lot."

MYTH: Vaccine-preventable diseases occur more often in vaccinated people than in unvaccinated people.

On its face, this statement is actually true. However, it is important to understand why it is true.

Let's take the situation of 100 young adults living in a college dormitory and say that 95 were vaccinated against measles and 5 were not vaccinated. An outbreak of measles strikes the college campus. In the dormitory, 6 of the 95 people who were vaccinated get measles, and 4 of the 5 unvaccinated people get measles. This would mean that vaccinated people get measles more commonly than unvaccinated people (in this case, by a margin of 6 to 4). However, the attack rate for measles in the unvaccinated group was 80 percent (4 of 5), whereas the attack rate for measles in the vaccinated group was only 6 percent (6 of 95). So, people were much less likely to get measles if they had received the measles vaccine.

Indeed, a study recently reported in the Journal of the American Medical Association found that unvaccinated people were 35 times more likely to get measles than vaccinated people.

MYTH: The hepatitis B vaccine causes arthritis, multiple sclerosis, and long-term (chronic) neurologic disorders.

A segment of the ABC show 20/20 told of children and adults who developed arthritis, multiple sclerosis, or neurologic disabilities following receipt of the hepatitis B vaccine. However, if one event precedes another, it did not necessarily cause the other.

For example, multiple sclerosis commonly has its onset in adolescence and early adulthood. Therefore, if the hepatitis B vaccine is given to adolescents and young adults, some will develop multiple sclerosis following receipt of the vaccine. For some, onset of multiple sclerosis could follow soon after receipt of the vaccine and appear to be related. But the only way to determine whether the hepatitis B vaccine caused multiple sclerosis would be to determine the incidence of multiple sclerosis in those who had received the vaccine and the incidence in those who hadn't received the vaccine.

Four studies have been performed to answer this question and all have reached the same conclusion: The incidence of multiple sclerosis was the same in those who received the hepatitis B vaccine and those who hadn't.

So, why is the hepatitis B vaccine blamed for all these problems? When children or adults suffer we search desperately for a cause. If we can find a clear, discrete cause, then at least we can help other people avoid what we have suffered. No clear cause for multiple sclerosis, autism, violent behavior, sudden infant death syndrome, hyperactivity, Alzheimer's disease, and many cancers have been found. It's frustrating. And vaccines are an easy target. But venting our frustrations by blaming vaccines, in the absence of any clear evidence that vaccines are the problem, will only endanger our children.

MYTH: Vaccines, if administered in the first two years of life, can cause diabetes.

One researcher claimed that infants immunized with a single dose of the Hib vaccine at 14 months of age were less likely to get diabetes than if they received four doses of the Hib vaccine at 3, 4, 6, and 14 months of age. He concluded that the risk of diabetes could be reduced if children did not receive vaccines at a young age. Some parents have seen this information and chosen to wait until 2 years of age to have their children immunized. This is unfortunate because some vaccine-preventable diseases, like Hib and pertussis, occur commonly in the first 2 years of life.

A careful review of the data, however, found that the analytic methods used in that study were incorrect. In addition, a 10-year follow-up study showed that the incidence of diabetes was the same in those who had been immunized early and in those who had been immunized later. So, no evidence exists to support the notion that vaccines should be delayed.

MYTH: The DTP vaccine causes a disease that looks like "shaken baby" syndrome.

Small children who are shaken forcefully in rage can develop bleeding around the brain (subdural hematomas) and bleeding on the back of the eye (retinal hemorrhages). Some lawyers have chosen to defend people accused of abusing children by saying that bleeding was caused by the pertussis component of the DTP vaccine. However, no evidence exists to support this contention. Neither pertussis nor the pertussis vaccine cause bleeding around the brain or on the back of the eye-only forceful shaking does this.

MYTH: The DTP vaccine caused deafness in the winner of the Miss America pageant in 1994.

The Miss America winner was supposedly rendered permanently deaf by a bad DTP vaccine-a story that got a lot of play in the news media in 1994. The story was totally false. However, her deafness followed a case of bacterial meningitis as a child. The cause of the meningitis was Haemophilus influenzae type b (Hib), a bacterium for which a vaccine became available in this country in 1990. Hib meningitis caused deafness in up to 20 percent of children in the past. Fortunately, the Hib vaccine has virtually eliminated Hib meningitis.

MYTH: The polio vaccine is the cause of AIDS.

Tom Curtis wrote an article in Rolling Stone magazine claiming that the origin of AIDS could be traced to poliovirus vaccines that were administered in the Belgian Congo between 1957 and 1960. The explanations behind this assertion were as follows: (1) All virus vaccines are made in cells, (2) the poliovirus vaccine was grown in monkey kidney cells, (3) monkey kidney cells used at that time contained a virus (simian immunodeficiency virus, or SIV) similar to the virus that causes AIDS (human immunodeficiency virus, or HIV), and (4) people were inadvertently inoculated with SIV, which then mutated to HIV and caused the AIDS epidemic.

This reasoning is confounded by several false assumptions. First, although monkeys can be infected by SIV, a disease similar to HIV, SIV is not found in kidney cells. Second, SIV and HIV, although their spelling is very similar, are not genetically very close; mutation to one from the other would require centuries, not years. Third, SIV and HIV, although deadly viruses, are fairly fragile. Both of these viruses, if given by mouth (in a manner similar to the oral polio vaccine), would be rapidly destroyed by the enzymes and acids in the mouth and stomach. Lastly, original lots of the polio vaccine were recently tested for the presence of HIV using very sensitive tests that were not available in the late 1950s. These tests, called polymerase chain reaction, or PCR, are used today to diagnose HIV infection in children, adolescents, and adults. No HIV was present in any of those lots.

MYTH: The polio virus vaccine is contaminated with a virus that causes cancer.

It is true that early lots of the poliovirus vaccine used in the late 1950s and early 1960s were contaminated with a monkey virus called simian virus 40, or SV40. Recently one investigator found proteins made by SV40 virus in unusual tumors in adults. The studies were suggestive enough that the National Institutes of Health continued to research the association. However, the initial observation has not been confirmed by subsequent studies.

In any case, none of the currently manufactured polio vaccines-neither the live vaccine given by mouth (OPV) nor the killed vaccine given as a shot (IPV)-contain SV40. Therefore, current poliovirus vaccines pose no risk of coming in contact with SV40.

MYTH: The pertussis vaccine isn't necessary. The incidence of pertussis was declining before we used pertussis vaccine in the United States.

The pertussis vaccine was introduced into the United States in the mid-1940s. Between 1900 and 1940, the incidence of pertussis was definitely declining. This decline was due to improved hygiene and sanitation.

However, the pertussis vaccine hastened the decline of the disease. There are five pieces of evidence that prove the vaccine's efficacy:

• In clinical trials of the pertussis vaccine, those who received the vaccine were protected against pertussis, whereas those who didn't receive it were not.
• Introduction of the pertussis vaccine into communities leads to a rapid decline in the incidence of pertussis.
• Pertussis recurs in countries in which the vaccine has been discontinued or immunization rates have declined.
• In communities where pertussis infection is common, the incidence of disease is greater in unimmunized children.
• When epidemics of pertussis occur, unimmunized children are more likely to get pertussis than immunized children.

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