Vaccine MYTHS

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 influenzae 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 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 people today have never seen a case of measles, mumps, German measles, polio, diphtheria, tetanus, or whooping cough. Some of these people 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!
• 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.

MYTH: Vaccines weaken the immune system.
Natural infection with certain viruses can indeed weaken the immune system. This means that when infected with one virus, some people can't fight off other viruses or bacteria as easily. This happens most notably in children, 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.
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.

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 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.