A Parent’s Guide to Understanding Vaccines Part II

In today’s digital age, information about vaccines is everywhere. With countless articles, social media posts, and videos circulating online, it can be challenging to separate science from misinformation. Myths about vaccines often spread faster than facts, leading to confusion and uncertainty among those seeking answers. In part II of our vaccine blog series, we’re addressing some of the most common questions and myths about vaccines. 

Are Vaccines Safe?

Yes! This question is an important one and was touched on in Part I of our vaccine blog series. Like any medical intervention, similar to most things in life, vaccines come with some potential risks. The most common vaccine side effects are mild, short-lived, and a sign that the body is building protection. For example, most vaccines can cause redness or tenderness at the injection site or low-grade fever. Other common side effects include fatigue, headache, or muscle aches. These usually appear within a day or two after vaccination and go away on their own without treatment.

In very rare cases, more serious reactions can occur. Examples of these include anaphylaxis, a severe allergic reaction, which occurs in approximately 1 to 2 cases per million vaccine doses. Febrile seizures, a type of seizure that occurs in children when they have a rapid rise in body temperature, can occur with any condition that causes fever, including after vaccines. While febrile seizures can be scary, they are a relatively common condition in childhood. As many as 5% of all children under the age of six will have a febrile seizure and they are most often caused by a viral illness. One 2019 study found that of more than 1000 children with a febrile seizure, less than 7% of these were following vaccinations (1). Children who have febrile seizures recover without complications in virtually all cases. Another rare reaction is Guillain-Barré Syndrome (GBS), a neurological condition that can occur very rarely after the flu vaccine, typically at a rate of about 1–2 cases per million vaccine doses. People can also develop GBS after having the flu or other viral illnesses. In fact, GBS occurs about 17 times more often from illness than after vaccination (2, 3). 

Understanding that “safe” doesn’t mean “zero risk” helps us make informed, realistic decisions about our health – just as we do when we drive a car, take medication, or even eat certain foods. As a pediatrician, I ask the question “Do the benefits of the vaccine outweigh the risks?” And for each of the vaccines recommended for children and adolescents, the answer is yes.

Common Vaccine Myths and the Truth Behind Them

MYTH 1. Vaccines Cause Autism

One of the most persistent and harmful myths is that vaccines, specifically the MMR (measles, mumps, rubella) vaccine, cause autism. This myth originated from a 1998 study by Andrew Wakefield, which has since been thoroughly discredited due to significant flaws in the study design (4). The original study was retracted, and Wakefield lost his medical license due to ethical violations. Multiple large-scale studies have since proven no link between vaccines and autism.

It is human nature to look for cause-effect relationships- when one event occurs before another, it is normal to question if they are related. For example, if your child tries a new food at dinner and sleeps poorly that night, you may ask- did the new food cause the poor sleep? But the answer is “no”.

The reality is that nearly all children receive vaccines- including children who have autism and children who do not. To claim that vaccines cause autism is false. It also oversimplifies what is known about the multifactorial causes of autism. For more information, visit the “Autism Speaks” website (5).

MYTH 2. Natural Immunity Is Better Than Vaccine-Induced Immunity

Natural immunity occurs when your child’s immune system builds protection after being infected with an illness or disease. When your child’s body encounters a virus or bacteria, it learns to recognize and fight it off, which can provide both short term and lasting immunity. However, gaining this immunity comes with a major catch: your child has to get sick first – and depending on the illness, that can be extremely risky.

For example, being infected with measles can lead to severe and long-term health consequences in children, including pneumonia, brain swelling (encephalitis), and long-term immune suppression- termed “immune amnesia”- which erases protection against previously encountered infections. In rare but fatal cases, especially in kids infected before age 2, the virus can persist in the nervous system and cause subacute sclerosing panencephalitis (SSPE), a devastating degenerative brain disease, even years later.

In contrast, vaccine-induced immunity gives your child’s immune system a controlled preview of a virus or bacteria through a harmless piece of it or a weakened form. This allows your child’s body to build defenses without the risk of suffering from the full-blown disease.

In short, while natural immunity can be strong, it comes at much higher cost and can potentially lead to life-threatening complications. Vaccine-induced immunity offers a much safer and more predictable way to gain immunity- without putting your child’s health, and the health of others, on the line.

MYTH 3. Vaccines Overwhelm the Immune System

Some people worry that the number of vaccines given during childhood is too much for the immune system to handle. However, your child’s immune system is incredibly powerful and capable of managing far more than the small number of pathogens (or “germs”) that they are exposed to through vaccines. In fact, children’s immune systems are exposed to countless germs daily just through normal interactions with their environment, such as touching objects, eating, or playing. In contrast, even when receiving several vaccines at once, a child is exposed to only a small fraction of the “germs” that they are exposed to on a daily basis.

MYTH 4. Vaccines Are Not Needed Because Vaccine-Preventable Diseases Are Rare

Thanks to vaccines, many diseases that once caused widespread illness and death, like polio, smallpox, and measles, are now rare or eradicated in many parts of the world. For example, measles was considered eliminated in the US in 2000 due to the widespread use of the safe and effective MMR (measles, mumps, rubella) vaccine. Unfortunately, falling vaccination rates among several communities across the country have led to a rapidly increasing number of measles cases (6). While the overall rates of measles vaccination remains high (>90%), the risk of contracting measles is growing; this is especially true for unvaccinated people, including those most vulnerable who cannot be vaccinated, such as young infants or people with certain medical conditions.

MYTH 5. Why Not Wait Until My Child is Older to Vaccinate? My Child Seems So Young for Vaccines.

This is a common question among parents, and it’s understandable. We all want to protect our tiniest humans and there are several reasons why it’s important that vaccines are given to infants and young children:

• Early Protection is Key: Infants and young children are some of the most vulnerable to serious and sometimes deadly diseases, and vaccines provide early protection during this critical time.
• Vaccines Schedules Are Designed for Maximum Effectiveness: The immunization schedule is specifically designed to provide the most effective protection at the optimal time for each vaccine. Many vaccines are given in a series, with doses spaced out to ensure long-lasting immunity. 
• Some Diseases Can Strike Quickly: Vaccination schedules are built around the fact that some diseases can spread rapidly, especially in environments where young infants and children interact, such as daycare centers or other play spaces. By vaccinating on time, you help protect your child from these diseases before an unexpected exposure occurs.
• Herd Immunity: Vaccinating your child also helps protect others in the community, especially those who cannot be vaccinated due to medical reasons, such as those with weakened immune systems. The sooner your child is vaccinated, the quicker they contribute to the collective protection of everyone around them.
• Young Immune Systems Are Smarter: We know that when we vaccinate children they maintain lifetime immunity. Waiting until kids are older, or even adults, sometimes means their vaccine protection doesn’t last as long. HPV vaccination is a great example of this. When children receive 2 doses before age 13 they have strong lifetime protection. After age 15, they need a third dose to receive the same protection.

The Bottom Line: Vaccines Are Safe and Effective

Vaccines are one of the most effective ways to prevent disease and protect public health. Global immunization efforts have saved more than 154 million lives over the past 50 years! While myths and misconceptions about vaccines are common, it’s important to understand the science behind vaccines. As your healthcare team, we encourage you to reach out if you ever have any concerns or questions.

References:

1. Deng L, Gidding H, Macartney K, et al. Postvaccination febrile seizure severity and outcome. Pediatrics 2019;143(5)e20182120. doi: 10.1542/peds.2018-2120
2. Influenza: The Disease & Vaccines | Children’s Hospital of Philadelphia
3. Vaccines and Guillain-Barré Syndrome | Children’s Hospital of Philadelphia
4. https://www.chop.edu/vaccine-education-center/vaccine-safety/vaccines-and-other-conditions/autism
5. What causes autism? | Autism Speaks
6. Measles Cases and Outbreaks | Measles (Rubeola) | CDC