Myths & Facts: Childhood Vaccines

IMMUNIZATIONS ARE one of the success stories of modern medicine, having eradicated smallpox, slashed child mortality rates and prevented lifelong disabilities. And as new viruses continue to threaten the public, protecting against these and long-standing illnesses will continue to be important in the decades and centuries ahead. 

Since the first vaccine was developed to prevent smallpox in the late 1700s, scientific advances have led to many more vaccine discoveries, especially during the first half of the 20th century when vaccines that protected against whooping cough (1914), diphtheria (1926), tetanus (1938), influenza (1945) and mumps (1948) came about. Thereafter, new manufacturing techniques allowed for vaccine production to be scaled up, setting global vaccination and disease eradication efforts in motion. In the second half of the 20th century, other vaccines were added to the list of those that could protect against viruses such as polio in 1955, measles in 1963 and rubella in 1969.¹

While both children and adults need vaccinations, the childhood vaccination schedule is vitally important. As vaccination rates rise, the entire population benefits from “herd immunity,” which occurs when a large part (typically between 83 percent and 94 percent) of the population is immune to a specific disease. Also, when children are vaccinated, they help prevent the spread of serious illnesses and protect vulnerable groups such as older adults and people with compromised immune systems. 

Today, the Centers for Disease Control and Prevention’s (CDC) Advisory Committee on Immunization Practices (ACIP) recommends children receive 10 vaccines in various doses from birth to 15 months old and another nine vaccines (some of which are the same) in various doses between 18 months and 18 years of age (Tables 1 and 2).²

Table 1. CDC Recommended Vaccinations Birth to 15 Months 

Table 2. CDC Recommended Vaccinations 18 Months to 18 Years

For children aged birth to 24 months, ACIP recommends vaccination against 14 potentially serious illnesses (Table 3).³

Fortunately, vaccination rates among children in the U.S. have remained relatively high. According to CDC, national coverage by age 24 months was greater than 90 percent for three or more doses of poliovirus vaccine, three or more doses of hepatitis B vaccine, more than one dose of varicella vaccine and more than one dose of measles, mumps and rubella vaccine (MMR), although MMR coverage was less than 90 percent in 14 states. Coverage with two or more doses of influenza vaccine was higher for children born during 2016-2017 (58.1 percent) than for those born during 2014-2015 (53.8 percent), but it was lowest among all vaccines studied. Only 1.2 percent of children had received no vaccinations by age 24 months.⁴

However, researchers from Kaiser Permanente who evaluated the uptake and coverage for recommended vaccines among nearly one million children aged birth through 18 years since the outbreak of COVID-19 found vaccine coverage continued to decline even after uptake recovered among certain age cohorts, causing the number of unvaccinated children to grow. “When vaccination rates decline, we worry about an increase in vaccine-preventable diseases that can be harmful to children,” said Bradley Ackerson, MD, a Kaiser Permanente South Bay Medical Center pediatric infectious disease specialist and an investigator with the Kaiser Permanente Southern California Department of Research & Evaluation’s vaccine team. “Also, we know there has been a reduction in childhood vaccinations worldwide, and as COVID-19 restrictions are relaxed, there will be an increased risk of outbreaks due to vaccine-preventable diseases among children returning from outside the United States, unless children here are vaccinated.”⁵

Regrettably, COVID-19 is only one reason many parents are reluctant to vaccinate their children. Rather, a growing number of parents are refusing to vaccinate due to persistent myths that have circulated for decades.

Separating Myth from Fact

Myth: Vaccine-preventable diseases are just part of childhood.

Fact: Vaccine-preventable diseases can be serious and lethal. While natural immunity — catching a disease and getting sick — results in a stronger immunity to a disease than a vaccination, the dangers far outweigh the benefits. In contrast, serious complications can be avoided through immunization. For example, if a child contracts measles, he or she would face a one in 500 chance of death from symptoms, whereas the number of people who have had severe allergic reactions from an MMR vaccine is less than one in a million.⁶ 

Consider these other statistics: About one person in 10 infected with diphtheria dies; approximately 100 people die each year from liver failure caused by hepatitis A; prior to the Haemophilus influenzae type b (Hib) vaccine, one child in four suffered permanent brain damage, and one in 20 died; prior to the MMR vaccine, about 48,000 children were hospitalized each year, 7,000 had seizures, about 1,000 suffered per­manent brain damage and about 450 died; and prior to the rotavirus vaccine, the disease caused more than 400,000 doctor visits, 200,000 emergency room visits, up to 70,000 hospitalizations and 20 to 60 deaths each year.⁷

Myth: Since vaccine-preventable diseases have been virtually eliminated, children really don’t need to be vaccinated.

Fact: It’s true vaccines have reduced most vaccine-preventable diseases to very low levels in many countries. However, some of them are still prevalent and even epidemic in other parts of the world, and travelers can unknowingly bring these diseases into any country. So, without vaccinations, these diseases can quickly spread throughout the population. In fact, relatively few cases of a disease could quickly become tens or hundreds of thousands of cases without protection from vaccines.⁸ 

And, importantly, there are people who cannot be vaccinated, including infants, pregnant women and immunocompromised people, and their only hope of protection is for people around them to be protected so they don’t spread the disease. This is known as herd immunity; for each infectious disease, a certain percentage of people in an area must be vaccinated to keep outbreaks at bay. This means children who can be vaccinated but aren’t are more likely to get sick if an outbreak occurs.⁹

Myth: Vaccines contain harmful ingredients.

Fact: Vaccines contain ingredients that allow the products to be safely administered. These ingredients include thimerosal (a mercury-containing compound), formaldehyde and aluminum. And, while these chemicals are toxic to the human body in certain levels, only trace amounts of them are used in U.S. Food and Drug Administration (FDA)-approved vaccines. On the other hand, people are naturally exposed to mercury in milk, seafood and contact lens solutions; formaldehyde is produced at higher rates by people’s own metabolic systems, and they are exposed to it through automobile exhaust, household products and furnishings, paint and felt-tip markers, and some health products; and the amount of aluminum in vaccines (approximately 0.125 mg to 0.625 mg per dose) is much less than what the average person consumes in a day (30 mg to 50 mg) in foods, drinking water and medicines.

In fact, the type of mercury used in vaccines, ethylmercury, is quite different from methylmercury, which is highly toxic and found in some seafood. In addition, ethylmercury leaves the body within a few days and poses no danger to children. In addition, many vaccines now produce single-dose vials, which has greatly decreased the use of thimerosal in vaccines. It’s also important to note that not all vaccines contain aluminum.^6,9,10

Myth: Vaccines can cause harmful side effects and even death.

Fact: All vaccines can cause side effects, but rarely are they serious, and so few deaths are attributed to vaccines that it’s hard to assess the risk. Most adverse effects are mild such as pain, swelling or redness where the shot was given, mild fever, chills, feeling tired, headache, muscle and joint aches and fainting. Most of these side effects are a sign the body is starting to build immunity (protection) against a disease. Serious side effects occur in only one per thousands to one per millions of doses. Signs of a severe allergic reaction can include difficulty breathing, swelling of the face and throat, a fast heartbeat, a bad rash all over the body, and dizziness and weakness. See Table 4 for the possible side effects of the routinely recommended vaccines.^11,12

Myth: Vaccines cause autism and sudden infant death syndrome (SIDS).

Fact: Science hasn’t yet determined the cause of autism and SIDS. The association between vaccines and these diseases is due to diagnoses made during the same age range that children are receiving their routine immunizations. And, while that may point to a causal connection, the logic is faulty. For instance, bread could be associated with car crashes since most drivers who crash cars could probably be shown to have eaten bread within the past 24 hours.^8,10 However, bread played no part in causing the crashes.

Fear was generated about the association between vaccines and autism after a study was published in The Lancet in 1998 that purported to link autism to the MMR vaccine, which children typically receive at 12 months and 4 years of age. But that study was ultimately debunked and retracted, and an overwhelming majority of experts agree vaccines don’t cause autism. In fact, Andrew Wakefield, the lead author of the discredited study, was forbidden to practice medicine in the United Kingdom in part because he falsified the study’s findings. Since that study was published, numerous other studies have found no connection between autism and vaccines.⁹

The DTaP vaccine is often linked to the cause of SIDS. But, similar to autism, most SIDS deaths occur during the age range when three shots of DTaP are given. And, when a number of well-controlled studies were conducted during the 1980s, investigators nearly unanimously found the numbers of SIDS deaths temporarily associated with DTaP vaccination was within the range expected to occur by chance, which means the SIDS deaths would have occurred even if no vaccinations had been given. And, in several of the studies, children who had recently received the DTaP vaccine were less likely to die from SIDS.⁸

Myth: Children can get the disease from the vaccine.

Fact: Yes and no, depending on the type of vaccine. Only vaccines made from live viruses or bacteria carry any risk of transmitting a disease, and even then, the risk is very small and symptoms are generally very mild. Most vaccines are inactivated (killed) vaccines, so it isn’t possible to contract the diseases from them.

There are several types of vaccines:¹³

• Attenuated vaccines are made from live viruses and live bacteria that have been weakened, usually by repeated replication in a lab. And, because these organisms are alive, it’s possible for them to cause a very mild form of the disease, but this happens very rarely. Doctors are cautious about giving live vaccines to anyone with a weakened immune system such as someone being treated for cancer. Four vaccines are made from live viruses: chickenpox (varicella), MMR, rotavirus and influenza (only nasal spray). None of the other vaccines on the immunization schedule, including the polio shot, are made from live viruses or bacteria. The oral polio vaccine is made from live viruses, but it is no longer administered in the United States.

• Inactivated or killed vaccines are made from bacteria or viruses that have been killed by heat or chemicals. These vaccines can’t cause the disease because the infectious agent can’t reproduce. However, the dead virus or bacteria is still enough to stimulate the body’s immune system. The flu shot and injected polio vaccine are inactivated vaccines.

• Component, or fractional or subunit, vaccines are inactivated vaccines made from just a part of the virus or bacteria. For the Hib vaccine, for example, part of the coating of the bacteria is introduced, which stimulates immunity against the bacteria. The hepatitis A and B vaccines and the pneumococcal vaccine are also component vaccines. Partial viruses and bacteria are unable to reproduce or cause disease.

• Toxoid vaccines contain a toxin or chemical made by the virus or bacteria, so they protect against the harmful effects of infection rather than the actual infection. These vaccines include the DTaP vaccine. Toxoid vaccines do not contain the virus or bacteria and cannot cause disease.

Most illnesses reported after receiving vaccines are due to the vaccines’ triggering an immune response to the disease, helping the body fight off and remember the germ so it can attack it if the germ invades again.

Myth: “Hot lots” of vaccines are associated with more adverse events and deaths.

Fact: Hot lots of vaccines are based on the presumption that the more reports of adverse events a vaccine lot is associated with, the more dangerous the vaccine is in that lot. But this is misleading because, for one, an adverse event report following vaccination doesn’t mean the vaccine caused the event. Statistically, a certain number of serious illnesses and deaths are expected to occur by chance among children recently vaccinated. Secondly, vaccine lots are not the same. Vaccine lot sizes may vary from several hundred thousand doses to several million, and some are in distribution much longer than others. A larger lot or one in distribution for longer will be associated with more adverse events. And, more coincidental deaths are associated with vaccines given in infancy because the background death rates for children are highest during the first year of life. Therefore, reviewing published lists of hot lots won’t help parents identify the best or worst vaccines.⁸

Myth: The proximity of multiple childhood vaccines increases the risk of harmful side effects and overloads children’s immune systems.

Fact: Recommendations for the age at which vaccines are administered are influenced by age-specific risks for disease, complications and responses to vaccination, and potential interference with the immune response by passively transferred maternal antibodies. Vaccines are generally recommended for members of the youngest age group at risk for experiencing the disease for which vaccine efficacy and safety have been demonstrated.¹⁴

CDC recommends vaccination providers adhere to recommended vaccination schedules to provide optimal protection. While some parents worry having so many vaccines in a short period early in life (children can get as many as 29 shots by age 6 years) can overwhelm their children’s immune systems, most experts agree it is unwise to space out vaccines since CDC bases the schedule on disease risks and vaccine effectiveness at specific ages and how the vaccines interact with each other. For instance, the MMR vaccine is timed so children receive it when they lose residual immunity from their mothers. Whereas an unvaccinated child has a nine in 10 chance of contracting measles if he or she walks into a room an infected person has recently left, a child with both recommended doses of MMR has only a 3 percent likelihood of developing measles.⁹

Myth: Any risk concerning vaccines is too risky to justify vaccination.

Fact: The benefits of vaccines are far greater than any risks. Without vaccines, there would be more cases of disease and more serious side effects and deaths. For example, according to an analysis of the benefit and risk of DTaP immunization, without an immunization program in the U.S., pertussis cases could increase 71-fold and deaths due to pertussis could increase fourfold. A child is far more likely to be seriously injured by one of these diseases than by any vaccine.⁸

Dispelling the Myths Now

Public health successes have been directly attributable to vaccines for the past 200 years. Yet, despite the proven lifesaving benefits of preventing diseases rather than treating them after they occur, challenges remain due to parental resistance. Reasons for vaccine resistance include individual rights and public health stances toward vaccination, religious standpoints and vaccine objections, and suspicion and mistrust of vaccines — all of which pose a significant public health problem. But suspicion and mistrust can be overcome. Candid communications between parents and clinicians can play a powerful role in whether parents choose to have their children vaccinated. And, it hinges on dispelling the plethora of myths surrounding vaccines.