Episode 10: Vaccine Safety Series 5 - Inside the vial: the truth about what’s actually in vaccines

For informational purposes only, please discuss getting vaccinated with your physician. Feel free to show them this podcast.

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Welcome back to my series devoted to helping parents sort through the propaganda and fear-mongering regarding vaccines.

Episode 5 clarifies what components vaccines actually contain and how we know they are safe. 

OK guys, it’s a good day for a good day! And have I got something to make your day even better! Boy do I! Information to protect yourself and your family from infectious diseases! Today, I’ve got the skinny on something that’s been coming up lately—What exactly is in a vaccine?

There’s a lot of anxiety out there. And to be honest, that anxiety is understandable. As a parent, your job is to protect your child. That protective instinct is powerful—and it should be. When you hear big chemical names or ingredients that sound more like something out of a chemistry textbook than a children’s medicine label, it’s natural to pause. You ask yourself: “Is this safe? Why is this in there? Why do kids need so many shots so early?” Those are fair questions and check out my episode on Too Many Too Soon to learn why it's not too many too soon.

The problem is, the loudest voices online aren’t always the most accurate. And in the age of social media, content that triggers fear and outrage spreads fast. A video shouting "vaccines contain poison" might get millions of views, while a peer-reviewed article calmly explaining the role of a stabilizer or adjuvant might barely reach anyone outside the science community.

But science doesn't work on likes and shares. It works on evidence, on rigorous testing, on time, and on transparency. And that’s what I want to bring you today—straightforward, science-based answers to some of the most common questions about what’s in vaccines.

BUT THEY HAVE CHEMICALS!

And here’s where it gets tricky: we live in a world where the word “chemical” is almost always framed as a negative. And scientific names, even for everyday substances, can sound alarming. But here’s the thing—everything is made of chemicals. Water is a chemical. Oxygen is a chemical. Even the sugars in fruit or the proteins in your child’s lunchbox are made of chemical compounds. What matters is the dose, the function, and the context.

Let’s use an example: formaldehyde. That word might immediately bring to mind something scary, like embalming fluid. But did you know that your own body produces formaldehyde as part of normal metabolism? It helps make amino acids and build DNA.

Endogenous formaldehyde & 1C Metabolism Sidebar: Endogenous means originating from within or not caused by external factors. So how does our body make formaldehyde? Folic acid is a B vitamin essential for various metabolic processes, including nucleotide synthesis and DNA replication. But folate, the natural form of vitamin B9, must be converted into tetrahydrofolic acid (THF) before it can be used in various cellular processes. Enzymes do the conversion and THF is referred to as a folate derivative – it is derived from folate. Folate derivatives can undergo oxidative breakdown—which means they are degraded by reactions with highly reactive molecules containing oxygen (reactive oxygen species (ROS)—and in the case of folate derivatives, oxidative breakdown results in release of formaldehyde.

And then our bodies detoxify it.

When formaldehyde is released in our bodies by metabolic processes, something called glutathione—a tripeptide (a molecule composed of three amino acids linked together by peptide bonds) composed of cysteine, glycine, and glutamic acid that is crucial in the body as an antioxidant and a detoxifying agent—reacts with formaldehyde to form S-hydroxymethylglutathione. An enzyme called ADH5 (alcohol dehydrogenase 5) then further processes it ultimately leading to the production of formate.

Formate sounds just as bad so let’s talk about that. Formate is an intermediate metabolite within one-carbon (1C) metabolism, which is a set of biochemical pathways that transfer one-carbon units between molecules. A one-carbon unit, also known as a C1 unit, is a single carbon atom or group that is transferred between molecules during metabolic reactions. These pathways are crucial for various cellular processes, including DNA and RNA synthesis, amino acid metabolism, and epigenetic regulation. Formate is made from reactions in 1C metabolism including from detoxification of formaldehyde. Formate is then further used in C1 metabolism or processed by the kidneys. If either enough formaldehyde or formate accumulated in our bodies, it would harm us, but our bodies deal with these processes efficiently and safely.

OK, so back to formaldehyde. We are exposed to natural sources of formaldehyde every day. And what we need to know regarding vaccines, is that the amount of formaldehyde in a vaccine is less than the amount naturally found in a pear. Yes—a pear. Scientists always say, the dose makes the poison, and that’s because it’s absolutely true. Too much water can kill you whether it’s breathed in or swallowed, right?

So that’s one example of a scary sounding chemical. My point isn’t that you shouldn’t ask questions. In fact, asking thoughtful questions is what good parents to do. The problem isn’t skepticism. The problem is when misinformation—or its more dangerous cousin disinformation—fills the gap left by unanswered questions.

Unfortunately, social media has created an environment where scientific nuance gets flattened. A headline might scream, “Toxic Ingredients Found in Vaccines!” without explaining that the “toxic” ingredient is present in amounts so small they can’t cause harm—and that it actually plays an important role in the vaccine’s function or stability.

When people say, “Why does a vaccine need anything other than the part that teaches the immune system what to fight?” the answer is: it’s complicated. Vaccines need to stay potent during storage. They need to be safe and effective in different populations. They need to trigger a strong enough immune response to offer real protection. That means they often contain ingredients that improve the vaccine’s performance or longevity.

Understanding what these ingredients are, and what they do, is how we begin to replace fear with facts. Because every ingredient in a vaccine is there for a reason—and those reasons are rooted in protecting your child from serious, preventable diseases.

CORE VACCINE COMPONENTS 

OK, so vaccines come in many forms depending on what type of antigen they use—the antigen is the pathogen or part of the pathogen that teaches your immune system to recognize it and be ready to defend against it if it invades. Types of vaccines include live-attenuated, inactivated, subunit, toxoid, mRNA, and viral vector, among others. Now, no matter the type of antigen or vaccine technology, vaccines contain the same basic categories of other non-antigen ingredients. As a whole, those non-antigen ingredients are called excipients.

Some excipients are added on purpose because they are needed and include:

• Adjuvants, to help stimulate a stronger immune response. For example, aluminum salts.

• Stabilizers, maintain the vaccine's effectiveness over time during transportation and storage. For example, sugars or gelatin.

• Preservatives, protect the vaccine from contamination and degradation. For example, thimerosal.

• Delivery Components, added to effectively get the antigens into the body.

  
  

Other excipients (often called residuals) are there only in trace amounts left over from the manufacturing process with as much removed as possible. These can include:

• Cell culture materials, used to grow the vaccine antigens. For example, egg protein, cell culture medium.

• Inactivating ingredients, used to kill viruses or inactivate toxins. For example, formaldehyde.

• Antibiotics, used to prevent contamination by bacteria. For example, neomycin.

Let’s explore each one in detail, using clear explanations, real-life analogies, and examples from actual vaccines used in childhood immunization schedules.

Antigen

The antigen is the centerpiece of the vaccine—the part that “trains” your immune system. Think of it as a wanted poster that lets your body know what the bad guy looks like. Once your immune system sees this poster, it starts creating tools—antibodies and memory cells—to recognize and fight that invader in the future.

Depending on the type of vaccine, the antigen might be:

• A weakened virus (like in MMR for measles, mumps, and rubella)

• A killed virus (like in the inactivated polio vaccine, or IPV)

• A protein subunit (like in the Hepatitis B or HPV vaccine)

• A toxoid—a deactivated bacterial toxin (as in diphtheria or tetanus vaccines)

• mRNA that teaches your body to make a harmless viral protein for training (like in the Pfizer and Moderna COVID-19 vaccines)

Each of these antigens has been carefully selected and tested to safely mimic part of the germ without causing illness. The result? Your body learns to recognize the real threat without ever being in serious danger.

Now let’s get into the Excipients

Adjuvants

Adjuvants are ingredients that enhance the body’s immune response to the antigen. Think of them as a microphone for the immune system—they help amplify the signal so your body can mount a stronger, longer-lasting defense.

The most common adjuvants are aluminum salts, like aluminum hydroxide or aluminum phosphate. These have been used safely in vaccines since the 1930s and are found in vaccines like DTaP (diphtheria, tetanus, pertussis) and Hepatitis B.

A common misconception is that aluminum is dangerous in vaccines. But here’s the truth: the amount used is tiny—often less than what a baby naturally gets from breast milk, formula, or even drinking water. Aluminum is actually one of the most abundant elements on Earth, and your body is equipped to process it.

Modern vaccines are now exploring newer adjuvants too. For example, the AS01 adjuvant system used in the shingles vaccine (and others) contains natural compounds derived from plants, combined with lipids to improve immune response. AS01 is a special ingredient added to some vaccines to help make them work better. It contains three main parts:

• MPL, a purified and weakened substance from bacteria that helps trigger the immune system,

• QS-21, a natural compound taken from the bark of a South American tree,

• Liposomes, tiny fat-like bubbles made with cholesterol that help deliver the other ingredients to the body more effectively.

Together, these help the vaccine create a stronger and longer-lasting immune response.

Adjuvants don’t stay in your body forever—they're either excreted or broken down. Their job is to kickstart your immune system’s training camp, then step aside.

Stabilizers

Stabilizers help keep the vaccine effective during storage and transportation. Vaccines are biological products, and like many biologics, they can degrade over time if they’re not protected from environmental changes like heat, light, or pH shifts. The stabilizers used in vaccines are chosen based on the molecular characteristics and structure of the antigen.

Common stabilizers include:

• Sugars, such as sucrose or lactose

• Gelatin, derived from pigs or cows

• Amino acids, like glycine

• Proteins, like human serum albumin (a purified, safe protein found in human blood)

These ingredients are like the packaging peanuts of the vaccine world—they keep the active ingredients from breaking down before they can do their job.

It’s important to note that gelatin and egg proteins have occasionally raised concerns about allergies. However, allergic reactions to these ingredients are extremely rare, and when necessary, alternative vaccines are available for people with known severe allergies.

Viral_vaccine_stabilizers_status_and_trends.pdf

Download PDF • 418KB

Preservatives

Preservatives prevent contamination of the vaccine, especially in multi-dose vials where the vaccine is accessed multiple times. Without preservatives, a vial that’s been opened could become contaminated with bacteria or fungi—and that could be dangerous.

Preservatives found in vaccines include:

• Phenol: Used in some typhoid fever vaccines.

• 2-Phenoxyethanol: Found in vaccines like polio, pneumococcal, and typhoid fever vaccines.

• Other Preservatives such as methylparaben, m-cresol, benzyl alcohol, and chlorobutanol have been considered or used in some vaccines.

Historically, though, the most talked-about preservative has been and remains thimerosal, a mercury-based compound used to prevent bacterial growth. And here why we don’t need to be scared of thimerosal. Thimerosal contains ethylmercury—a form of mercury that is rapidly cleared from the body and is not the same as toxic methylmercury—despite it being absolutely safe, it’s been largely discontinued in childhood vaccines since the early 2000s, mostly to address public concern, not because of evidence of harm.

Today, most vaccines for children contain no thiomersal at all. Some multi-dose flu vaccines may still contain it, but single-dose versions are widely available.

Another on the list I mentioned is 2-phenoxyethanol, which is used in vaccines like IPOL (inactivated polio) and DTaP. It has a long safety record and is also used in even higher concentrations in baby wipes and cosmetics.

Delivery Components (Lipids, Emulsifiers, and More)

Newer vaccine technologies, like mRNA vaccines, require additional components to deliver the active ingredient into your body’s cells.

For instance, lipid nanoparticles are used in the Pfizer and Moderna COVID-19 vaccines. These are tiny fat-like bubbles that protect the fragile mRNA and help it enter cells, where the immune system can start recognizing and responding to the protein it encodes. I have an entire episode on mRNA vaccines and recommend checking it out!

Other vaccines use emulsifiers or surfactants, like polysorbate 80, to ensure that the ingredients mix properly and remain evenly distributed. Polysorbate 80 is also used in ice cream and salad dressings, and it has a long record of safe use in injectable medicines.

These delivery components are essential for the vaccine to work. Without them, the antigen wouldn’t reach the right place in your body—or might break down before it ever gets there.

Residuals

Residuals are trace amounts of substances used in the manufacturing process but not added intentionally to the final vaccine. These are leftovers from growing the vaccine’s components or from purifying and preparing the antigen.

Examples include:

• Egg protein, from growing flu viruses in eggs

• Formaldehyde, used to inactivate viruses or toxins

• Antibiotics, like neomycin, to prevent bacterial contamination during production

• Yeast proteins, from growing certain vaccine antigens

These substances are present in incredibly small amounts—often measured in micrograms or nanograms. To give you a sense of scale, that’s like a grain of sand in an Olympic-sized swimming pool.

Again, the amounts are well below safety thresholds and are carefully monitored in every batch.

So, to recap: every component in a vaccine has a job to do.

• The antigen is the trainer.

• The adjuvant is the coach, making sure the training sticks.

• Stabilizers keep the vaccine strong and effective through distribution.

• Preservatives protect the vaccine from contamination.

• Residuals are minute traces from the production process, tightly regulated and tested for safety.

• And delivery agents, like lipids or surfactants, help the vaccine get where it needs to go in your body.

None of these ingredients are filler. None are random. They’re all carefully chosen, thoroughly tested, and continuously monitored—because the goal is always the same: to protect you and your child from serious, preventable diseases.

And now let’s put this in the context of real world vaccines.

REAL WORLD VACCINE EXAMPLES

I’m not going to go into every vaccine, but the FDA has a page listing all vaccines licensed for use in the US with links to details including package inserts for each one. Immunize.org also has a page listing all vaccines in use with package inserts. You know enough now to be able to look at the Description section of those inserts (where the ingredients will be) and understand what you’re reading. If you have specific questions about something you see in a vaccine not covered here, let me know!

1. MMR Vaccine (Measles, Mumps, Rubella)

The MMR vaccines protects against three serious viral illnesses:

• Measles: a highly contagious disease that can cause fever, cough, rash, and lead to complications like pneumonia, brain swelling, and death.

• Mumps: causes swollen salivary glands, fever, and can lead to hearing loss or testicular inflammation.

• Rubella: generally mild in children but can cause severe birth defects if a pregnant woman is infected.

There are two MMR vaccines available in the United States: M-M-R II® (Merck & Co.) and PRIORIX® (GlaxoSmithKline Biologicals) and they are considered interchangeable. M-M-R II® has been licensed in the US since 1978 and has been used extensively in >75 other countries, with >803 million doses distributed globally as of May 2021, we don't have newer stats on its use. M-M-R II® is licensed as M-M-RVaxPro, in the UK (since 1997) and in the EU (since 2005).  PRIORIX® was licensed in the EU in 1997, in the UK in 2006, and in the US in 2022. Those can be given to people of all ages.

Globally, the most common MMR vaccines used today are M-M-R II® (aka M-M-RVaxPro) and PRIORIX®. So I’ll focus on those.

Type of Vaccine: Live attenuated virus — uses weakened viruses as antigen

Ingredients:

Antigen—the pathogen or part of the pathogen—in this case three viruses—that elicits the immune response.

• M-M-R II® (aka M-M-RVaxPro) contains a live attenuated strain of measles virus, derived from Enders' attenuated Edmonston strain; the Jeryl Lynn™ (B level) strain of mumps virus; and the Wistar RA 27/3 strain of live attenuated rubella virus.

• PRIORIX® contains the attenuated Schwarz strain of measles; the RIT 4385 strain of mumps (derived from Jeryl Lynn strain); and Wistar RA 27/3 strain of rubella.

Adjuvant—a substance that enhances the body's immune response to an antigen

• Measles vaccines don't need an adjuvant so they don't contain any.

Stabilizers to help the vaccine maintain its effectiveness while the vaccine is made, stored, and moved. MMR vaccines do need stabilizers:

• M-M-R II® (aka M-M-RVaxPro) contains sorbitol, sucrose, and hydrolyzed gelatin.

• PRIORIX® contains lactose, mannitol, and sorbitol.

Preservative to protect the vaccine from outside bacteria or fungus.

• Lyophilized (freeze-dried) MMR vaccines do not need preservatives, so they don't contain any.

Delivery Components: None in either MMRII® or PRIORIX®

Residuals: Remember residuals are byproducts of manufacturing with no medicinal properties and are taken out after production. The very small amounts of these ingredients that remain in the final product are so small there's no way they could be harmful.

• M-M-R II® (aka M-M-RVaxPro) contains minute levels of recombinant human albumin (≤0.3 mg), fetal bovine serum (<1 ppm), approximately 25 mcg of neomycin and other buffer and medium ingredients.

• PRIORIX® contains minute amounts of neomycin.

Both lyophilized vaccines are reconstituted in sterile water.

Why the vaccine matters: Before the MMR vaccine, measles alone caused hundreds of deaths per year in the U.S. Outbreaks are resurging in some communities due to declining vaccination rates and we've already has 3 measles deaths this year in the US. The MMR vaccine is safe, highly effective, and has prevented millions of cases and deaths globally.

2. DTaP Vaccine (Diphtheria, Tetanus, acellular Pertussis)

This combination vaccine protects against three potentially deadly bacterial infections:

• Diphtheria: causes a thick coating in the throat and breathing problems.

• Tetanus: causes painful muscle stiffness and can be fatal.

• Pertussis (whooping cough): can cause violent coughing fits and is especially dangerous in infants.

There are two DTaP vaccines used in the United States: Adacel® and Boostrix®. The FDA approved both Boostrix® and Adacel® for use during pregnancy. They are both sterile suspensions of antigens for intramuscular injection.

Type of Vaccine: Toxoid (for diphtheria, tetanus, and pertussis ) and acellular subunit (pertussis)

Ingredients

Antigens:

• Adacel® (Sanofi Pasteur) uses tetanus toxoid, diphtheria toxoid, and acellular pertussis antigens (individual pertussis proteins that will elicit an immune response including detoxified pertussis toxin, and three proteins that help pertussis stick to your cells: filamentous hemagglutinin, pertactin, and fimbriae)

• Boostrix® (GlaxoSmithKline) contains tetanus toxoid, diphtheria toxoid, and inactivated pertussis toxin and formaldehyde-treated filamentous hemagglutinin and pertactin.

Adjuvants:

• Adacel®: aluminum phosphate

• Boostrix®: aluminum hydroxide

Antigens are adsorbed onto the adjuvants in these vaccines as is done with the anthrax vaccine, which I talk about in the anthrax episode.

Stabilizers:

• Adacel®: 2-phenoxyethanol

• Boostrix®: aluminum hydroxide

Preservative: Both Adacel® and Boostrix come in single dose vials or syringes and so do not need or contain preservatives.

Delivery Components: 

• Adacel®: None

• Boostrix®: polysorbate 80 (Tween 80) is used as an emulsifier, to keep the ingredients mixed together.

Residuals: 

• Adacel®:

  • formaldehyde from inactivating the diphtheria and tetanus toxins

  • glutaraldehyde to inactivate the pertussis toxin

  • filamentous hemagglutinin and pertactin are treated with formaldehyde

  • sodium chloride (salt) from salt precipitation during production.

• Boostrix®:

  • formaldehyde from inactivating the diphtheria and tetanus toxins

  • glutaraldehyde and formaldehyde to inactivate the pertussis toxin.

  • filamentous hemagglutinin and pertactin are treated with formaldehyde

  • sodium chloride (salt) from salt precipitation during production

Only miniscule amounts remain after sequential filtration, ultrafiltration, and chromatography are used to purify the vaccine.

Why the vaccine matters: Each of these diseases once caused widespread illness and death. DTaP helps protect young children during their most vulnerable years and reduces disease circulation in the community.

3. IPOL® (Inactivated Polio Vaccine)

Polio is a viral disease that can lead to paralysis or death. It’s been nearly eradicated worldwide thanks to mass immunization efforts. The inactivated polio vaccine used in the US is called IPOL® and is a sterile suspension of three types of poliovirus: Type 1 (Mahoney), Type 2 (MEF-1), and Type 3 (Saukett).

Type of Vaccine: Inactivated virus 

Ingredients:

Antigens: inactivated poliovirus types 1, 2, and 3

Stabilizer: 2-phenoxyethanol

Preservatives: 2-phenoxyethanol and formaldehyde

Residuals:

• formaldehyde (used in inactivation)

• antibiotics (neomycin, streptomycin, and polymyxin B) from production

• calf bovine serum albumin from production cell culture

• M199 medium is used to dilute the concentrated viral suspensions to get the target antigen levels

SIDEBAR Medium 199: 

What is M199?

M199 (Medium 199) is a special nutrient solution created in the 1950s to help grow cells in labs. Think of it like a "vitamin water" for cells—it gives them the nutrients they need to survive and grow when scientists are working with them outside the body. M199 was originally created to be a clean, precisely defined cell nutrient solution without any animal ingredients, making it especially useful for virus research and the large-scale production of vaccines.

What’s in it?

It contains a mix of:

• Salts (like those in your body) to keep cells balanced,

• Amino acids (building blocks of proteins),

• Sugars for energy,

• Vitamins like B1 and B2

• other small molecules to support cell health.

It doesn't have proteins or growth hormones, so sometimes these are added separately depending on what the cells need.

How is it used?

M199 is often used in vaccine development and virus research. It helped grow the cells needed to develop early polio vaccines and is still used today to help make vaccines safely and in large amounts.

Why is it important?

M199 is ideal for clean, controlled cell growth because it was designed to be free of animal products. This makes it safer and more consistent for things like making vaccines or testing new medicines.

Why the Polio Vaccine matters: Before polio vaccines, outbreaks paralyzed tens of thousands of children every year. IPOL is safe, highly effective, and a cornerstone of global public health success.

WTF-RFK

RFK has been going all-in spreading common misconceptions and fears about vaccine components, so let’s clear some things up. What does the science actually tell us?

First of all he said recently that kids die every year from measles vaccine and that is total, utter, 100% bullshit. No death has ever been causally linked to the measles vaccine. Ever. You know what DOES kill kids? Measles. Please see my measles episode for everything you want to know about measles.

Now, you know who is vaccinated against measles? RFK, his kids, and his grandkids. RFK runs the antivax movement with Andrew Wakefield and Del Bigtree. He founded the antivax Children’s Health Defense. He makes money on antivax lawsuit referrals and alternate treatments. He’s also a eugenicist who thinks people with money and power are the ones worth giving healthcare to. He wants an autism database so he knows who to target. Call your representatives. His appointment to head of HHS is a betrayal of American public health. And get your vaccines while you have access because with him in charge they will be going away. He's already targeting updated flu and covid vaccines with his policies. This is no joke. OK, end rant.

So, let's address his recent outrageous lie:

“There are aborted fetal cells in vaccines!”

This one sounds dramatic but is a misrepresentation of how some vaccines are made. Here’s the truth:

Fetal fibroblast cells (WI-38 and MRC-5) used to grow vaccine viruses were first obtained from elective termination of two pregnancies in the early 1960s. Crucially, these fetal cells were never used directly in vaccines. Instead, they were cultured and grown in labs to create cell lines—self-replicating populations of cells that have been maintained under controlled conditions for decades. These cell lines are not fetal tissue. They are generations removed from the original cells and behave like standard laboratory cell cultures. No ongoing supply of fetal tissue is needed to maintain them.

The reason these cells are used is that they’re excellent at growing viruses—especially for viruses that only replicate well in human cells. After the virus is grown, it’s purified and the final vaccine contains no cells and no fetal tissue. This method is used in the development of vaccines like rubella, hepatitis A, and varicella.

The Vatican, the U.S. Conference of Catholic Bishops, and other religious authorities have issued statements clarifying that receiving these vaccines is morally acceptable when no alternatives are available.

"All vaccinations recognized as clinically safe and effective can be used in good conscience with the certain knowledge that the use of such vaccines does not constitute formal co-operation with the abortion from which the cells used in production of the vaccines derive.”

Vatican Statements on Vaccinations.docx.pdf

Download PDF • 40KB

His other lies:

“Vaccines contain antifreeze!”

This myth stems from confusion between two different compounds: ethylene glycol and polyethylene glycol (PEG).

Ethylene glycol is the toxic chemical found in antifreeze. Polyethylene glycol, on the other hand, is a completely different compound. It’s used in many medications and is a common ingredient in laxatives, including products like Miralax. PEG is used in mRNA vaccines to help stabilize lipid nanoparticles—the fat bubbles that deliver the mRNA into your cells.

PEG has been studied for decades. It’s been used in injectable medications, cosmetics, and other products. Allergic reactions to PEG are extremely rare, and the amount used in vaccines is very small. So no, vaccines do not contain antifreeze.

“Formaldehyde in vaccines kills people?”

Formaldehyde is used during the manufacturing process to inactivate viruses or detoxify bacterial toxins. Trace amounts may remain in the final vaccine.

Here’s the key point: formaldehyde is also produced naturally by your body. It’s essential for making amino acids and DNA. You’ll find more formaldehyde in a pear or in your own bloodstream than you will in any vaccine.

The amount used in vaccines is far below toxic levels, and it’s been thoroughly studied. The real danger isn’t in the vaccine—it’s in the fear that spreads when scientific context is removed.

“Aluminum causes brain damage.”

This concern often cites studies about high levels of aluminum in industrial or environmental settings—not the minuscule amounts used in vaccines.

Aluminum salts are used as adjuvants to enhance the body’s immune response. They’ve been used safely in vaccines for over 70 years. The amount in a single dose is about 0.125 to 0.85 milligrams, which is much less than what babies ingest from breast milk, formula, or food over a week.

Extensive studies have looked at aluminum exposure from vaccines and found no link to developmental issues, autism, or neurological harm. The body processes aluminum efficiently, and the small amounts used in vaccines are well within safe limits.

SAFETY AND SURVEILLANCE of vaccines

OK, so now let’s talk about something that often gets overlooked in vaccine conversations: what happens after a vaccine is developed and approved. This is where vaccine safety monitoring and surveillance systems come in—and they’re a big reason why vaccines are among the most closely monitored medical products in the world.

It’s easy to assume that once a vaccine is approved, it’s just sent out into the world and forgotten about. But the truth is quite the opposite. Vaccine safety oversight is ongoing, transparent, and multi-layered.

Let’s start at the beginning.

Before approval, vaccines go through multiple phases of testing:

• Preclinical studies in labs and animals help identify potential benefits and risks.

• Phase 1 clinical trials involve small groups of healthy volunteers to assess basic safety and dosing.

• Phase 2 trials include more participants and gather additional data on safety, immune response, and optimal dosing.

• Phase 3 trials involve thousands—sometimes tens of thousands—of people to confirm effectiveness and monitor for side effects across a broad population.

These trials follow strict ethical and scientific standards, and they’re reviewed by independent oversight boards and regulatory agencies like the FDA in the U.S. And this rigorous process leads to vaccine recommendations which are updated regularly.

But approval is only the beginning of safety monitoring. Once a vaccine is in widespread use, multiple systems continue to track its safety in real-time.

Post-marketing surveillance systems include:

VAERS (Vaccine Adverse Event Reporting System):

• Run by the CDC and FDA, VAERS allows anyone—doctors, nurses, patients, parents—to report health issues that happen after vaccination.

• It’s an early warning system. If multiple people report the same unexpected issue, it prompts further investigation.

• VAERS is not proof that a vaccine caused a problem. It’s a way to detect patterns that may require scientific follow-up.

VSD (Vaccine Safety Datalink):

• This is a partnership between the CDC and several large healthcare organizations.

• It uses electronic health records from millions of people to track vaccine outcomes in near real-time.

• Researchers can look at trends, compare vaccinated vs. unvaccinated groups, and assess potential risks statistically.

Clinical Immunization Safety Assessment (CISA) Project:

• A CDC initiative involving experts in vaccine safety who provide individual case evaluations and guidance to clinicians.

• CISA also helps study vaccine safety in specific populations, like people with rare medical conditions.

Global Surveillance:

Organizations like the World Health Organization (WHO) and European Medicines Agency (EMA) conduct global monitoring of vaccine safety.

This international collaboration helps detect very rare side effects that might only appear once a vaccine is used on a massive scale.

Outside the US it’s often referred to as: AEFI (Adverse Events Following Immunization) monitoring. 

Unfortunately, the US-based websites above are currently being revised as per the new antivax administration so I recommend not using them at this time and instead using WHO or other international sources for accurate information on vaccines.

What happens when a potential safety signal is detected?

It triggers a cascade of responses:

• Independent experts review the data.

• Additional studies may be launched.

• Regulatory agencies may issue warnings, update guidance, or even pause distribution temporarily—as we saw with the Johnson & Johnson COVID-19 vaccine when a rare blood clotting condition emerged.

This isn’t a sign that the system is failing. It’s a sign that the system is working. It shows that vaccine safety isn’t static—it’s constantly reevaluated with every new piece of data.

Let’s be clear: vaccines are not risk-free. No medical intervention is. But the risks from vaccines are typically very small—especially when compared to the risk from the diseases they prevent. For example:

• The risk of a severe allergic reaction (anaphylaxis) from a vaccine is about 1 in a million. For a deep dive into this listen to my episode on the Vaccine Court.

• The risk of hospitalization from measles? About 1 in 4. And complications like brain swelling or death occur in roughly 1–2 per 1,000 cases.

Transparency and public communication

Another important feature of vaccine safety systems is transparency. Did you know that in the U.S., every meeting of the Advisory Committee on Immunization Practices (ACIP) is open to the public and livestreamed? The data, debates, and recommendations are documented and available online. Again, I anticipate the antivax head of HHS will be turning these into antivax free-for-alls, so we need to be careful. But before him accurate information has been available.

This kind of transparency is rare in medicine. But it’s baked into vaccine policy because public trust depends on openness. Scientists and regulators know this—and they take it seriously.

You can even read the full prescribing information for any vaccine, including ingredients, known side effects, and clinical trial results. It’s all published. Nothing is hidden. And reports on the CDC website that were written and published before Jan 20 are legit. For example, here is the measles updated report published Nov, 18, 2022. Let’s see how long that stays up.

So, vaccine safety is not a one-time check mark. It’s a continuous process involving:

• Preclinical research

• Multi-phase clinical trials

• Post-approval surveillance

• Global data sharing

• Independent advisory committees

The goal isn’t just to make vaccines safe—it’s to keep them safe, even as new data emerge and as they’re given to millions of people with diverse health backgrounds.

So the next time someone says, “We don’t know what the long-term effects of vaccines are,” you can say: “Actually, we’ve been studying vaccines longer and more intensively than almost any other product in modern medicine.”

Because vaccine safety is a process that never stops.

BOTTOM LINE

Vaccines are one of the most impactful public health tools in human history. They’ve prevented millions of deaths, reduced suffering, and helped us eradicate or control diseases that once caused widespread devastation. In fact, according to the World Health Organization, vaccines prevent an estimated 4 to 5 million deaths each year globally. That’s not theory. That’s reality.

Let’s take a moment to appreciate what that really means. Before vaccines, diseases like diphtheria, measles, and polio were constant threats. Parents worried their children might not survive childhood. Schools would close during outbreaks. Hospital wards were filled with kids in iron lungs because of polio-induced paralysis.

Today, because of vaccines, many parents have never had to witness these horrors. In fact, vaccines have been so successful that some people question whether we even need them anymore. But that’s like saying we don’t need umbrellas because we’re not getting wet—it’s the very protection that makes the danger seem distant. And that distance is exactly why the antivax movement is even a thing. Being antivax is a luxury brought to you by…vaccines.

And I want to remind you here that vaccines don’t just protect the individual; they protect entire communities, a concept known as herd immunity. When a large portion of the population is immune, it becomes difficult for a disease to spread. This is especially important for people who can’t be vaccinated—like newborns, people with certain allergies, or those undergoing cancer treatment. These individuals rely on the immunity of those around them.

It’s also worth remembering that vaccine-preventable diseases can come back. We’ve seen this with measles outbreaks in areas with low vaccination rates. We’ve seen pertussis resurge when booster shots were missed. The pathogens haven’t disappeared—they’re just being held at bay by the wall of protection vaccines provide.

Every vaccine on the schedule represents a disease we’ve studied, understood, and learned to prevent. Every shot given is a quiet act of protection—a barrier against something we no longer want to see return.

So, get vaccinated. Get your children vaccinated. Help us preserve the progress we’ve made against some of the most dangerous diseases known to humankind.

Thanks for staying with me through this deep dive into what’s in vaccines. If you’ve made it this far, you’re clearly someone who cares—about facts, about health, and about protecting kids from preventable disease. So let’s wrap up by pulling everything together.

Vaccines aren’t mysterious potions made behind closed doors. They’re meticulously crafted tools based on decades of scientific knowledge, global collaboration, and rigorous safety standards. Every component—whether it’s an antigen, an adjuvant, a stabilizer, or a delivery molecule—serves a specific, necessary purpose. There’s no filler. There’s no fluff. Each ingredient is carefully tested, continuously monitored, and transparently disclosed.

If you’re a parent, you’ve probably had moments of worry. Maybe you’ve seen a viral post with scary claims or overheard someone in a waiting room question what’s in that little vial. Those moments can plant seeds of doubt—even in science-minded people. That’s okay. Questioning is part of being a good parent. But the next step is key: seeking out trustworthy information.

My hope is that this episode has helped bridge that gap between concern and clarity. You now know that aluminum in vaccines is measured, purposeful, and safe. That formaldehyde is a naturally occurring part of your own biology. That vaccines aren’t loaded with hidden toxins, but rather filled with carefully chosen components to teach your immune system how to fight without making you sick.

You’ve also learned that vaccines don’t just protect your child—they create a ripple effect of safety across your entire community. You’ve seen that myths—while often emotional and compelling—fall apart under the weight of evidence. And you’ve seen that the immune system is not something vaccines “override,” but something they train, support, and strengthen.

I will continue my vaccine safety series with episodes going in-depth on all the other vaccine misconceptions not yet covered and I will also do an episode on how vaccines work with your immune systems, go into more depth on herd immunity, and talk about why using sterilizing immunity as a metric for vaccine success is the dumbest thing we’ve had come out of COVID. Stay tuned for those.

For now, if someone asks, “What’s actually in a vaccine?” you’ll be ready—not just with facts, but with perspective. If you’re still curious, I encourage you to talk with your pediatrician, read from sources like the WHO, or Immunization Action Coalition. These are places where science is centered and fear takes a backseat.

And if this episode helped you, I’d love for you to share it. Maybe it answers a question for another parent. Maybe it helps counter misinformation in your circle. Because this is how we build trust, protect public health, and keep each other safe.