Vaccine myths unraveled

Note: This is the second of three blog posts on vaccines, written by interns and researchers in the Center for Health and Biosciences at the Baker Institute.


By Mohini Bindal
Research Assistant, Center for Health and Biosciences

Jonathan LeBeau
Intern, Center for Health and Biosciences

Melissa Martinez
Intern, Center for Health and Biosciences


There are many misconceptions about vaccines that are having detrimental effects on the well-being of Americans. Here, we elaborate on scientific research to refute a few of these popular myths.

Myth #1: Vaccines do not work

One method of gauging the potency of a vaccine is to compare the prevalence of a disease prior to the introduction of the vaccine to that after the vaccine was introduced.

For example, according to the Division of Viral Hepatitis, a subsection of the Centers for Disease Control and Prevention, there was a staggering decrease in Hepatitis A cases in the US since the introduction of the Hepatitis A vaccine in the mid-1990s. Prior to the introduction of the vaccine, an estimated 270,000 cases were reported annually in the 1980s in the US. In 2015, there were only 1,390 cases; in 2016, only 2,007. This is a 95% decrease in the number of cases reported annually compared to the early 1980s. Most recently, about 11,000 cases were reported in the US in 2018, which is higher than in recent years due to the increasing number of individuals not vaccinating their children.

Another example is the polio vaccine, created for the poliovirus which can cause lifelong paralysis. First introduced in 1955, the polio vaccine has significantly reduced the number of polio cases worldwide. In 1953, there were 57,000 cases of polio. Since 1979, this number has been reduced to zero in the US, except for the few cases of disease-carrying travelers from other countries. Other similar cases include vaccines for smallpox, diphtheria, whooping cough, and measles. These vaccines have significantly reduced the number of cases of infection since their introduction into our population. In fact, smallpox has been eradicated worldwide thanks to vaccines.

Conversely, if it were true that vaccines do not work, there would be no concurrent change in the health of the population as vaccination rates fell. However, the data indicate that as vaccination rates fall, the incidence of the associated disease drastically increases. For example, unfound fear of the whooping cough vaccine in the 1970s led to decreased vaccination rates in Great Britain, Japan, and Sweden, three developed countries. In subsequent years, all three countries faced surges in the incidence rate of pertussis, leading to the death of several children.

Thus, it goes to show that vaccines aid in the decreased transmission of diseases and subsequent eradication. Furthermore, eliminating vaccination or even decreasing it can lead to the reemergence of once eradicated diseases.

Myth #2: Vaccines contain harmful ingredients

Many sources claim that vaccines contain a cocktail of harmful ingredients. These arguments specifically mention Thimerosal, a mercury based preservative used in multi-dose vials of medicine and vaccines. However, this ingredient was proven to produce no harm to the human body. Moreover:

“Thimerosal was taken out of childhood vaccines in the United States in 2001. Measles, mumps, and rubella (MMR) vaccines do not and never did contain thimerosal. Varicella (chickenpox), inactivated polio (IPV), and pneumococcal conjugate vaccines have also never contained thimerosal. Influenza (flu) vaccines are currently available in both thimerosal-containing (for multi-dose vaccine vials) and thimerosal-free versions.” (Centers for Disease Control and Prevention)

After four independent epidemiological studies examining the frequency of neurobehavioral disorders following vaccination of thimerosal-containing vaccines, the World Health Organization (WHO) concluded that there existed no safety concerns for infants receiving these vaccines. The organization further stated that two previously published studies showing a reduction in neurobehavioral disorders following the discontinuation of thimerosal-containing vaccines were not substantive due to procedural flaws.

Myth #3: Vaccines cause major illnesses and even death

Andrew Wakefield, the British doctor who published a study claiming a link between the MMR vaccine and autism, was discredited and stripped of his credentials. His study was retracted by the Lancet following an investigation that highlighted an experimental design flaw. The investigation also uncovered a conflict of interest, which may have compromised the researcher’s professional judgement and influenced him to favor certain experimental outcomes over others. In fact, since the incident there have been numerous studies concluding that no substantive link between vaccines and autism exist. Other studies further determined that vaccine ingredients, particularly thimerosal, do not cause autism.

Similarly, some people mistakenly believe the Diphtheria-pertussis-tetanus (DPT) vaccine causes Sudden Infant Death Syndrome (SIDS). However, this mistaken belief is a result of the confounding variable, age, as most SIDS deaths occur around the age range that children are administered the DPT vaccine. In fact, research studies conducted since 1991 found no increased risk of SIDS following DPT vaccination. On the contrary, DTP immunization may actually aid in decreased SIDS mortality.

Further substantiating the argument against this myth, a survey conducted by the Australian Institute of Health and Wellness noted that in one section of the country, only 52% of five-year old children were vaccinated compared to the national rate of 92.9%. This smaller section of the country suffered higher rates of child mortality and cancer, as well as lower overall life expectancy, relative to that of the rest of the Australian population.

Myth #4: Natural immunity is more effective than vaccination

If this were the case, there would be a larger decrease in the incidence of a disease prior to the introduction of the vaccine compared to that after. As mentioned in Myth #1, historical trends show that vaccines are associated with a decrease in the incidence of disease.

Some speculate that improved living conditions, including hygiene, sanitation, and nutrition, are plausible rationales for the disappearance or decrease in incidence of some diseases. However, while it cannot be denied that superior living conditions have contributed to these results, historical trends reveal a decline in the frequency of a disease immediately after the introduction of the vaccine for that disease. Therefore, it cannot be denied that vaccines also play a role.

Finally, if natural immunity and improved hygiene were superior to vaccination, we would expect a greater decline in the number of reported cases of a disease in the absence of vaccination than when vaccination is present. However, history proves this is not the case. The previously described pertussis case in Europe is one example. Another example is the Soviet Union’s major diphtheria epidemic in the 1990s following a decrease in children immunization rates and adult boosters. In 1989, during vaccine use, there were only 839 cases of diphtheria. After vaccines were cease in 1994, there were 50,000 cases and 1,700 deaths by diphtheria.

Clearly, vaccines are substantially more effective than natural immunity.

Myth #5: Diseases that vaccines protect against have disappeared

The diseases themselves will never completely disappear; however, it is thanks to vaccines that we see exponential decreases in transmission of diseases and reported cases. The best example of this is seen with polio. Since the introduction of the vaccine, polio has been eradicated in the Western Hemisphere and countless other countries due to global initiative. Nevertheless, there remain regions in the world that have not been equally successful. Without vaccines, travelers from these regions could incite the transmission of polio in previously polio-free countries. It is due to continued vaccination that we have not seen a resurgence of this disease in the United States.

Myth #6: Too many vaccines are unhealthy for children

Recent studies were conducted to analyze the risk of injecting children with multiple vaccines and childhood illnesses. These studies found no causal relationship between multiple vaccines and a weakened immune system. Particularly, it was noted that multiple vaccines do not cause Type 1 diabetes, an increase in allergies, or multiple sclerosis.

Therefore, too many vaccines do not cause children to experience harmful side effects.

Myth #7: Vaccines are dangerous because they infect my child with the disease

Vaccines do not infect the person being vaccinated with the disease. Instead, each type of vaccine contains the pathogen or part of the pathogen in such a form that it will not cause the person to fall ill. For a more extensive explanation, see our previous article here. There are multiple types of vaccines, and each type has its own share of advantages and disadvantages. Rest assured, scientists have performed extensive research to ensure that vaccines are not harmful to people who take them.

Myth #8: Vaccines do not work because I still got the flu

The flu virus is an incredibly versatile microbe, able to change its shape to avoid detection in our bodies. In fact, the flu virus responds to the antibodies that our bodies produced in a process called antigenic drift. Thus, every year, scientists engage in the challenging task of staying ahead of the rapid evolutionary cycle of the virus and create a vaccine for the new strain. This process is carried out via several trials to ensure that the vaccine can effectively protect against the more deadly strains of the virus expected to be prevalent in the population for the coming year. However, sometimes people are be exposed to a strain of the flu that is very different from the expected virus for which the vaccine was created. In such cases, this is not a reflection of the efficacy of the flu vaccine that you received.


Read the first post, Vaccines: The Truth.