More Options

Answering Vaccine Skeptics

SkepDoc's Corner

Harriet Hall

June 14, 2017

The anti-vaccine movement is full of conspiracy theorists who deny the evidence for the effectiveness of vaccines, call vaccines “poisons,” think doctors and manufacturers (in collusion with the government) only promote vaccines to boost their incomes, and blame vaccines for all manner of adverse events. These vaccine denialists must not be confused with vaccine skeptics, many of whom are intelligent, well-educated people who trust science but who have legitimate questions and concerns about one or more vaccine. Many of these concerns turn out to be myths promulgated by people who appear to be experts and who sound convincing but who are not reliable sources of information. It’s hard for laymen, and even for many doctors, to distinguish the trustworthy sources of information from the untrustworthy. Here are some short answers to some of the most common objections to vaccines.

My Child Is Not Likely to Be Exposed to These Diseases

That’s true. This is actually a very good reason not to vaccinate, but it’s short-sighted. Vaccines have been so successful that these diseases are no longer around. Even if the risk of side effects with a vaccine are small, why expose your child to that small risk when the risk of catching the disease is even lower? And why waste your money and let your child experience the pain of a needle stick? The problem is that these diseases are only a plane-ride away, and your child could be exposed to an imported case; but that risk is still admittedly small. The bigger problem is that herd immunity protects everyone so these diseases are not likely to spread if a case is imported into a community. If enough people followed your reasoning and refused vaccination, herd immunity would decline and sooner or later these diseases would come roaring back. It is selfish and immoral to let others take a risk you are unwilling to take and then take advantage of the herd immunity those others have established. Vaccination is a social responsibility; it protects the community as a whole and protects vulnerable individuals who are too young to be vaccinated or who are at high risk like the elderly, people with chronic illnesses, and the immunocompromised (for instance, patients on chemotherapy).

Vaccines Cause Autism

A few years ago, there was legitimate concern that vaccines might cause autism, based in part on a since-retracted study by Andrew Wakefield. While a few studies may have suggested a correlation, we now have many more large, well-designed studies that have looked hard for a link between vaccines and autism or other neurodevelopmental problems and have failed to find one. The scientific consensus is clear: there is no credible evidence that vaccines cause autism.

There’s Toxic Mercury in Vaccines

This concern is particularly misguided, since there never was any mercury in the MMR vaccines that were falsely accused of causing autism, and there is no longer any mercury (thimerosal) in any vaccine except for multidose vials of flu vaccine, where it is used as a preservative to prevent contamination once the seal has been breached. Most flu vaccines given in the US are the single-dose version, and you can specifically request it, but there’s no reason to. There never was any evidence that thimerosal in vaccines caused any harm to recipients, and the World Health Organization (WHO) still strongly supports using thimerosal to allow lower-cost multidose vials to be used.

There Are Other Toxic Ingredients in Vaccines

Aluminum is used in some vaccines to enhance the immune response; the amount is less than everyday intake from foods, and the aluminum in vaccines has never been shown to cause harm. Formaldehyde is used in the manufacturing process and then removed; small traces may remain, but the amounts are too small to have a toxic effect. Rachael Dunlop has pointed out that you get 600 times more formaldehyde from eating a pear than you get from a vaccine, and your own body naturally produces formaldehyde. The “monkey virus” SV40 contaminated some polio vaccines half a century ago, but it did not cause any harm to recipients, and today’s vaccines are carefully screened to prevent such contamination. The viruses for some vaccines are grown in eggs or on chick embryo cell lines, so egg allergy has been a concern, but the amount of egg protein in most vaccines is so small that they can be given safely to most patients with egg allergies.

More Vaccinated People Get the Disease

Yes, but only because more people are vaccinated. The rate of illness is much higher in the unvaccinated than in the vaccinated. Vaccines are not 100 percent effective, but when vaccinated people catch the disease they are likely to have a milder illness.

Vaccines Can Overwhelm a Child’s Immune System

When parents see their child get several immunizations at a time, they naturally suspect that must not be a good thing. They assume that the current vaccine schedule is “too many, too soon.” But vaccines can’t overwhelm the immune system; they simply exercise it. Children encounter up to 6,000 immune challenges in their environment every day, compared to 150 during the course of the entire vaccine schedule. They can handle it. Delaying or spacing out vaccines only prolongs the period of vulnerability to the diseases.

The Diseases Were Already Going Away; Vaccines Had Nothing to Do with It

Anti-vaxxers love to show a graph demonstrating that the diseases were already going away before the introduction of vaccines, due to improved hygiene, sewers, safe water, etc. But that’s terribly misleading. The graph shows that the death rate was declining, not that the diseases were going away. The death rate was declining because of better medical care: not as many people who caught the disease died. But the number of people who caught the disease had not declined. Other graphs that show the incidence of the diseases are compelling: they show a precipitous drop after the introduction of vaccines. And there have been many inadvertent natural experiments in several countries where the vaccination rate dropped, the disease rate rose, and then the disease rate dropped again when the vaccination rate improved.

Vaccines Didn’t Eradicate Smallpox

They most certainly did! The last case occurred in Somalia in 1977. Some people claim that it is still around and is being misdiagnosed as chickenpox, but that’s absurd. Doctors can easily tell those two diseases apart on clinical grounds as well as by electron microscopy and blood tests. Vaccines wiped smallpox off the face of the Earth and are well on their way to eradicating polio and measles. In fact, every contagious disease that is transmitted only from person to person and has no environmental reservoir has the potential to be permanently eradicated like smallpox.

Vaccines Spread Disease

You’ve all heard people say, “The flu vaccine gave me the flu.” That’s a false assumption. It may have been a flu-like illness from another virus, or it may have been flu from a strain not covered in that year’s vaccine. You can’t get flu from the vaccine because it is prepared from only a small piece of the virus, and that piece is not infectious.

Some vaccines contain live viruses, but these are attenuated, weakened forms of the virus. They can replicate in the host to stimulate an immune response, but they can’t cause the disease. The varicella vaccine can cause a vesicular skin rash, which can transmit the attenuated vaccine virus to other people through direct contact, but this has happened only six times in 56 million doses, and it can be avoided by avoiding direct contact with the skin lesions. The oral polio vaccine is cheaper and easier to administer than the injectable vaccine and is the best choice for getting control of the disease in a population. It is a live virus that, even though it is attenuated, can sometimes spread to others and can rarely (one in 2.7 million) cause paralysis; for that reason, nations switch to the safer injectable vaccines once the disease is no longer prevalent.

Vaccines Aren’t Adequately Tested

All vaccines have to be rigorously tested in thousands of people before they are released; the approval process can take up to ten years, and monitoring continues after approval. The one exception is the flu vaccine. It’s not necessary to test each new annual formulation because it is the same vaccine only with antigens for slightly different strains of flu virus. If we waited to test each year’s formulation, it would not be available in time to protect people from the strains circulating that year.

Childhood Diseases Aren’t Serious

Many of us had those childhood diseases before vaccines were available, and for most of us the diseases were mild and didn’t cause any permanent damage. But these diseases can be serious and even fatal. We may not remember how polio paralyzed children and confined them to iron lungs. We may not have sat helplessly at the bedside of a child with diphtheria struggling to breathe or a child coughing uncontrollably from whooping cough until they choke, turn purple, and vomit. We may never have seen chickenpox develop into chickenpox pneumonia or kill an immunocompromised patient. We may not have seen a grandparent die from pneumonia as a complication of the flu. We may not have met anyone with brain damage from measles. We may not realize that one in ten thousand patients with measles will develop subacute sclerosing panencephalitis (SSPE), sometimes as long as fifteen years later, with a uniformly fatal outcome within three years of onset. One in 10,000 may seem like a small risk, but why take that risk when you can get insurance against it by getting the vaccine?

Vaccines Are Cultured on Cell Lines from Aborted Fetuses

Certain cell lines originated from human fetal tissue obtained from three elective abortions performed for medical reasons in the 1960s. No further fetal tissue has been obtained since that date. The Catholic church finds no moral or religious objection to the use of existing vaccines.

The HPV Vaccine Will Make My Children Promiscuous

This has been tested. Children who got the vaccine were not more likely to engage in sexual intercourse.

The HPV Vaccine Has Killed Thirty-Two (or 100) Young Women

This is a myth that has been thoroughly debunked on Snopes. The HPV vaccine has never killed anyone. Some young women have died after getting the HPV vaccine, but there is no evidence that anyone has ever died because of the vaccine. Alarmist death claims are based on reports to the VAERS (Vaccine Adverse Event Reporting System). VAERS is a voluntary reporting system that accepts reports of anything and everything that happened after a vaccination. The reports of deaths have been investigated, and analysis has not shown any causal link. Adverse events were no more common in vaccine recipients than in a comparable group of non-recipients.

Immunization Is Unnatural

Diseases are natural. They kill people. ’Nuff said.


Some intelligent and well-educated people question vaccines. They may have legitimate reasons to mistrust the medical establishment on other issues. They may have a strong emotional bond to a community that mistrusts vaccines, and they may tend to let emotions outweigh facts. They may have been persuaded by the so-called “evidence” and the myths promulgated by anti-vaccine activists and untrustworthy anti-vaccine scientists. Even some doctors and scientists are unable to distinguish between misleading anti-vaccine claims and good science.

Vaccine skeptics want what we all want: to keep our children safe. We mustn’t blame them or insult them for their concerns about vaccines. But we can give them accurate information to counteract the myths. Every objection to vaccines has been answered and thoroughly demolished by reputable doctors and scientists, but some people may not have seen the answers or may not trust them. I’ve only hit some of the highlights here. Many more details can be found in the Australian government publication “Myths and Realities: Responding to Arguments against Vaccination.” It’s an invaluable, exhaustive reference for anyone who has concerns about vaccines or wants to reassure others who have concerns.

Harriet Hall

Harriet Hall's photo

Harriet Hall, MD, a retired Air Force physician and flight surgeon, writes and educates about pseudoscientific and so-called alternative medicine. She is a contributing editor and frequent contributor to the Skeptical Inquirer and contributes to the blog Science-Based Medicine. She is author of Women Aren’t Supposed to Fly: Memoirs of a Female Flight Surgeon and coauthor of the 2012 textbook Consumer Health: A Guide to Intelligent Decisions.