Vaccine Reference Guide
Natalie's Clinical Study & Findings · Ingredients, Side Effects & Adverse Event Rates
This is a working reference covering the routine US vaccine schedule from infancy through adulthood. For each vaccine you'll find: what it prevents, key ingredients (the ones patients most often ask about), common side effects with rates from clinical trials, and serious adverse event rates from post-marketing surveillance. Data is drawn from package inserts, CDC/ACIP recommendations, and the FDA. A note on framing: every medical intervention carries some risk. The right way to evaluate a vaccine is by comparing the risk of vaccination to the risk of the disease it prevents — not by comparing it to zero.
Glossary of Terms
| Term | Definition |
|---|---|
| Adjuvant | A vaccine ingredient that enhances and prolongs the immune response. Classic example: aluminum salts. Without adjuvants, vaccines often require higher antigen doses and more shots to generate protection. |
| Antigen | The piece of the pathogen the immune system responds to — whole killed virus, protein fragment, bacterial toxin (toxoid), or mRNA instructions to make a protein. |
| Acellular | "Without whole cells." Acellular pertussis vaccines use purified pieces of the bacterium, far less reactogenic than the older whole-cell version. |
| Reactogenic | How much a vaccine causes immune-activation symptoms (sore arm, fatigue, fever, body aches). Higher reactogenicity reflects a stronger immune response — not more danger. Shingrix is famously reactogenic. |
| Inactivated vaccine | Made from a killed virus or bacterium that cannot replicate. Examples: inactivated polio (IPV), hepatitis A, most flu shots. |
| Live attenuated | Made from a weakened live pathogen. Replicates briefly to generate strong immunity; cannot cause the actual disease in healthy people. Examples: MMR, varicella, FluMist, rotavirus. |
| Subunit / recombinant | Contains only specific proteins from the pathogen, grown in cell culture or yeast. Examples: hepatitis B, HPV (Gardasil), Shingrix, acellular pertussis. |
| Conjugate vaccine | Protein-attached vaccine that helps young immune systems respond to bacterial sugars. Examples: Hib, PCV (Prevnar), meningococcal conjugate. |
| Toxoid vaccine | Made from inactivated bacterial toxin. The body learns to neutralize the toxin without exposure to the live bacterium. Examples: tetanus, diphtheria. |
| mRNA vaccine | Delivers genetic instructions in a lipid nanoparticle telling cells to briefly produce a viral protein. mRNA is destroyed within days; it does not enter the nucleus or alter DNA. Examples: COVID-19 mRNA vaccines. |
| Excipient | Any non-active ingredient — adjuvants, preservatives, stabilizers, manufacturing residuals. Anything other than the antigen itself. |
| VAERS | Vaccine Adverse Event Reporting System. Passive surveillance — anyone can report any health event after vaccination. A VAERS report is not proof of causation; it flags signals for controlled investigation. |
| VSD | Vaccine Safety Datalink. Active CDC surveillance using real medical records from millions of patients across multiple healthcare systems. Designed to actually quantify risks, unlike VAERS. |
| ACIP | Advisory Committee on Immunization Practices. The CDC committee that recommends which vaccines should be given and to whom. |
| Pertussis | Whooping cough. Bacterial respiratory infection (Bordetella pertussis) causing severe prolonged coughing. Dangerous for infants — can cause apnea, pneumonia, encephalopathy, and death. |
| DTaP vs. Tdap | Both are tetanus + diphtheria + acellular pertussis vaccines. DTaP is the higher-dose pediatric formulation. Tdap is the adolescent/adult booster with smaller diphtheria and pertussis components. |
What's Actually in Vaccines
Vaccine ingredients fall into a few functional categories. Almost every ingredient people ask about is one of the following. Quantities are typically in micrograms (µg) or nanograms (ng) — not the milligram-and-above doses associated with oral medications.
Aluminum Salts (Adjuvant)
| Component | Details |
|---|---|
| What it is | Aluminum hydroxide, aluminum phosphate, or aluminum potassium sulfate. Used as adjuvants since the 1930s. |
| Dose per shot | 0.125 to 1.5 mg aluminum. |
| Context | A breastfed infant ingests ~7 mg aluminum from breast milk over 6 months; formula-fed infants ~38 mg; soy-formula infants ~117 mg. Aluminum is the 3rd most common element in Earth's crust — found in food, water, soil, antacids, and antiperspirants. |
| Pharmacokinetics | Excreted by the kidneys. Concern is justified in premature infants on long-term IV nutrition or severe kidney disease where elimination is impaired. In healthy individuals, body burden from vaccines is a tiny fraction of dietary intake. |
| Found in | DTaP, Tdap, Td, HepA, HepB, Hib (some), HPV, PCV, MenB, Shingrix. |
| NOT found in | MMR, varicella, rotavirus, nasal flu, most injected flu vaccines, IPV alone, mRNA COVID-19 vaccines. |
Thimerosal (Preservative — Ethylmercury)
| Component | Details |
|---|---|
| What it is | Mercury-based preservative preventing bacterial/fungal contamination of multi-dose vials. |
| Status today | Removed from all routine childhood vaccines in the US in 2001 as a precautionary measure. Still present in some multi-dose flu vials. Single-dose flu, all childhood vaccines, MMR, varicella, IPV, Hib, HepA, and HPV are thimerosal-free. |
| Key biochemistry | Contains ethylmercury (half-life ~7 days, rapidly excreted) — biologically distinct from methylmercury in fish (half-life ~50 days, bioaccumulates). Conflating the two is a common error. |
| Autism question | The original 1998 Wakefield paper was retracted for fraud; Wakefield lost his medical license. Subsequent studies in millions of children across multiple countries found no association between thimerosal and autism, ADHD, tics, or developmental disorders. |
Formaldehyde (Manufacturing Residual)
| Component | Details |
|---|---|
| What it is | Used during manufacturing to inactivate viruses and detoxify bacterial toxins. Most is removed; trace amounts remain. |
| Typical residual | 50–100 micrograms per dose. |
| Context | The human body naturally produces ~50,000 µg of formaldehyde per day as a metabolic byproduct. A pear contains more formaldehyde than a vaccine. Per FDA, a newborn's circulating formaldehyde level is 50–70× higher than what a single vaccine could provide. |
| Cancer risk | Known carcinogen at chronic high airborne occupational exposure. No evidence linking trace vaccine amounts to cancer. |
Other Excipients
| Ingredient | Details |
|---|---|
| Polysorbate 80 | Emulsifier keeping ingredients evenly mixed. Also in ice cream, salad dressing, oral medications, and IV drugs. Allergic reactions rare. |
| 2-Phenoxyethanol | Preservative replacing thimerosal in some multi-dose vaccines. Used in cosmetics, some baby wipes, pharmaceuticals. |
| Gelatin / sorbitol | Stabilizers maintaining potency during storage. Gelatin derived from pork or bovine collagen — relevant for severe gelatin allergies and some dietary/religious considerations. Found in MMR, varicella, MMRV, some flu vaccines. |
| Trace antibiotics | Neomycin, polymyxin B, gentamicin, streptomycin used during cell-culture manufacturing. Present at nanogram levels. Penicillin and cephalosporins are never used due to allergy concerns. |
| Egg protein | Some flu vaccines and yellow fever vaccine produced in eggs. Most egg-allergic patients can now receive flu vaccine per current ACIP guidance. Egg-free flu alternatives: Flublok (recombinant), Flucelvax (cell-based). |
| Lipid nanoparticles / PEG / mRNA | mRNA vaccines contain mRNA wrapped in lipid nanoparticles including polyethylene glycol (PEG). mRNA degrades within days; does not enter the cell nucleus or alter DNA. PEG is the most common cause of the rare allergic reactions (~2–5 cases per million doses). |
| MRC-5 / WI-38 cells | Some viruses grow only in human cells. Two cell lines from elective abortions in the 1960s have been used for decades to grow vaccine viruses (rubella, varicella, HepA, rabies, others). Vaccines do not contain fetal cells — only trace residual cellular DNA. The Vatican and most major Christian denominations have concluded public health benefit justifies use given historical distance. |
Routine US Vaccine Schedule
The schedule below reflects current ACIP/CDC recommendations. Some vaccines are given as combinations (e.g., Pediarix combines DTaP + HepB + IPV; ProQuad combines MMR + varicella).
| Age / Timing | Vaccines |
|---|---|
| Birth | Hepatitis B (1st dose) |
| 1–2 months | Hepatitis B (2nd), DTaP, Hib, PCV, IPV, Rotavirus |
| 4 months | DTaP, Hib, PCV, IPV, Rotavirus |
| 6 months | DTaP, Hib (some), PCV, IPV, HepB, Rotavirus (some), Influenza (annual start) |
| 6 months – 5 yrs | RSV monoclonal antibody (nirsevimab) for first RSV season |
| 12–15 months | Hib (final), PCV (final), MMR, Varicella, Hepatitis A (1st) |
| 15–18 months | DTaP (4th dose) |
| 18–24 months | Hepatitis A (2nd dose) |
| 4–6 years | DTaP (5th), IPV (4th), MMR (2nd), Varicella (2nd) |
| 11–12 years | Tdap, HPV (2-dose series), Meningococcal ACWY (1st) |
| 16 years | Meningococcal ACWY (booster), Meningococcal B (shared decision) |
| Annual (6 mo+) | Influenza; COVID-19 (per current ACIP guidance) |
| Pregnancy | Tdap (each pregnancy, 27–36 wks), RSV, Influenza, COVID-19 |
| 50+ years | Shingrix (2 doses, 2–6 months apart) |
| 65+ years | Pneumococcal (PCV15/20 ± PPSV23); RSV (shared decision 60–74; recommended 75+) |
| Every 10 years (adults) | Td or Tdap booster |
Individual Vaccines
Each entry covers what the vaccine prevents, key ingredients, common side effects (from clinical trials), and serious adverse events (from post-marketing surveillance). Rates shown are population averages; individual risk depends on age, immune status, and medical history.
Hepatitis B (HepB)
Brand names: Engerix-B, Recombivax HB, Heplisav-B (adult), PreHevbrio (adult)
Prevents: Hepatitis B virus — acute and chronic liver infection, cirrhosis, liver cancer. Transmitted through blood, body fluids, and mother-to-baby at birth.
Ingredients
- Type
- Recombinant subunit (yeast-grown HBsAg protein)
- Adjuvant
- Aluminum hydroxide or aluminum hydroxyphosphate sulfate (~0.25–0.5 mg)
- Other
- Yeast protein (residual), sodium chloride, phosphate buffers, formaldehyde trace (some brands)
Common Side Effects
Sore injection site (~30%), fatigue (~14%), headache (~13%), low-grade fever (1–6%). Typically resolve in 1–2 days.
Serious Adverse Events
Anaphylaxis ~1 per 1.1 million doses. No causal link to chronic conditions (MS, autism, SIDS) despite extensive study.
Rotavirus (RV)
Brand names: RotaTeq, Rotarix
Prevents: Rotavirus gastroenteritis — before vaccination, hospitalized ~55,000–70,000 US children per year; remains a leading cause of childhood death globally.
Ingredients
- Type
- Live attenuated, given orally
- Adjuvant
- None (live vaccine, no aluminum)
- Other
- Sucrose, sodium citrate, sodium phosphate, sodium hydroxide, polysorbate 80, cell culture media
Common Side Effects
Mild diarrhea (~24%), vomiting (~15%), irritability, low-grade fever, decreased appetite. No injection site reaction.
Serious Adverse Events
Intussusception: ~1–5 additional cases per 100,000 vaccinated infants in the first week after dose 1. Much lower rate than the withdrawn RotaShield (1999). Severe allergic reaction very rare.
DTaP — Pediatric
Brand names: Infanrix, Daptacel; combos: Pediarix, Pentacel, Kinrix, Quadracel, Vaxelis
Prevents: Diphtheria (severe airway infection), tetanus (lockjaw), pertussis (whooping cough). Acellular formulation replaced whole-cell DTP in the 1990s — far less reactogenic.
Ingredients
- Type
- Toxoid (D, T) + acellular subunit (aP)
- Adjuvant
- Aluminum hydroxide or aluminum phosphate (~0.33–0.625 mg)
- Other
- Formaldehyde (≤100 µg residual), polysorbate 80, glutaraldehyde (trace), 2-phenoxyethanol, bovine extract (some brands)
Common Side Effects
Sore arm/redness/swelling (20–40%), low-grade fever (5–15%), fussiness, drowsiness, decreased appetite. Local reactions increase with successive doses.
Serious Adverse Events
Febrile seizure (~1 in several thousand) — no long-term harm. Hypotonic-hyporesponsive episode rare. Anaphylaxis ~1 per million. Persistent inconsolable crying >3 hours: ~1 in 1,000.
Hib (Haemophilus influenzae type b)
Brand names: ActHIB, Hiberix, PedvaxHIB
Prevents: Hib bacterial infections — meningitis, epiglottitis, pneumonia, sepsis. Before this vaccine, Hib was a leading cause of childhood meningitis with significant mortality and neurologic disability.
Ingredients
- Type
- Conjugate (bacterial polysaccharide attached to a carrier protein)
- Adjuvant
- Aluminum hydroxyphosphate sulfate in PedvaxHIB; none in ActHIB
- Other
- Sucrose, sodium chloride; tetanus toxoid carrier (some brands)
Common Side Effects
Sore injection site (~25%), low-grade fever (~5%). Generally well-tolerated.
Serious Adverse Events
Anaphylaxis very rare. No causal link to other serious conditions in extensive surveillance.
Pneumococcal Conjugate (PCV13/15/20)
Brand names: Prevnar 13, Vaxneuvance (PCV15), Prevnar 20, Capvaxive (PCV21, adult)
Prevents: Streptococcus pneumoniae — pneumonia, meningitis, bacteremia, otitis media. Each successive version covers more serotypes.
Ingredients
- Type
- Conjugate (polysaccharide + CRM197 carrier protein)
- Adjuvant
- Aluminum phosphate (~0.125 mg)
- Other
- Polysorbate 80, succinate buffer, sodium chloride, soy peptone (residual)
Common Side Effects
Sore arm (~30–60%), fever (~25% in infants), irritability, decreased appetite, drowsiness.
Serious Adverse Events
Severe allergic reaction < 1 per million. Febrile seizure rare, especially noted when co-administered with flu vaccine in young children. No long-term harm from brief seizures.
Inactivated Polio Vaccine (IPV)
Brand names: IPOL; combo products (Pediarix, Pentacel, Kinrix)
Prevents: Poliovirus types 1, 2, 3. Polio causes paralysis and was endemic in the US until vaccination programs eliminated it in 1979.
Ingredients
- Type
- Inactivated (killed) virus
- Adjuvant
- None alone; aluminum present in combo products
- Other
- Formaldehyde (residual), 2-phenoxyethanol, neomycin/polymyxin B/streptomycin (trace), bovine serum albumin (trace)
Common Side Effects
Sore injection site (~15–30%), redness, low-grade fever (~5%). Among the better-tolerated childhood vaccines.
Serious Adverse Events
Severe allergic reaction extremely rare. The oral polio vaccine (OPV) carried ~1 in 2.4 million risk of vaccine-derived paralysis; it has not been used in the US since 2000. IPV does not carry this risk.
MMR (Measles, Mumps, Rubella)
Brand names: M-M-R II; combo with varicella: ProQuad (MMRV)
Prevents: Measles (highly contagious — pneumonia, encephalitis, death), mumps (orchitis, meningitis, deafness), rubella (devastating birth defects if contracted in pregnancy).
Ingredients
- Type
- Live attenuated
- Adjuvant
- None
- Other
- Sorbitol, sucrose, hydrolyzed gelatin, sodium chloride, neomycin (trace), human serum albumin, MRC-5 cellular protein, sodium phosphate
Common Side Effects
Sore injection site, low-grade fever (~5–15%, peaks 7–12 days post-dose as live attenuated virus replicates), mild rash (~5%), transient joint pain (~25% in adult women), swollen lymph nodes.
Serious Adverse Events
Febrile seizure ~1 per 3,000–4,000 first doses (higher with MMRV than separate MMR + varicella). Transient ITP (low platelets) ~1 per 30,000–40,000, usually self-resolving. Encephalitis <1 per million — far lower than measles itself (~1 per 1,000 cases). Does not cause autism — definitively studied in millions of children.
Varicella (Chickenpox)
Brand names: Varivax; combo: ProQuad (MMRV)
Prevents: Varicella zoster virus (chickenpox). Reduces but does not eliminate later shingles risk.
Ingredients
- Type
- Live attenuated
- Adjuvant
- None
- Other
- Sucrose, hydrolyzed gelatin, urea, sodium chloride, monosodium glutamate, neomycin (trace), MRC-5 cellular protein
Common Side Effects
Sore injection site (~20%), fever (~15%), mild varicella-like rash near injection site (~3%) or generalized mild rash (~1–5%) within 5–26 days.
Serious Adverse Events
Disseminated vaccine-strain varicella in severely immunocompromised patients — vaccine contraindicated in this group. Transmission of vaccine virus to close contacts very rare and only if vaccinated person develops a rash. Severe allergic reaction very rare.
Hepatitis A
Brand names: Havrix, Vaqta; combo with HepB: Twinrix
Prevents: Hepatitis A virus — acute liver inflammation, typically transmitted via contaminated food or water.
Ingredients
- Type
- Inactivated
- Adjuvant
- Aluminum hydroxide or aluminum hydroxyphosphate sulfate
- Other
- Formaldehyde (trace), MRC-5 cellular protein, neomycin (trace), polysorbate 20, amino acids
Common Side Effects
Sore arm (~50%), headache (~15%), loss of appetite (~10%), fatigue. Most reactions mild, lasting 1–2 days.
Serious Adverse Events
Anaphylaxis very rare. No causal link to other serious conditions.
Influenza (Annual)
Brand names: Fluzone, Fluarix, Flucelvax, Flublok, Afluria, FluMist (nasal), Fluad (adjuvanted, 65+), Fluzone High-Dose (65+)
Prevents: Seasonal influenza A and B viruses. Reformulated each year based on circulating strains.
Ingredients
- Type
- Inactivated (most); live attenuated nasal (FluMist); recombinant (Flublok)
- Adjuvant
- Most flu vaccines: none. Fluad: MF59 (squalene-based adjuvant)
- Other
- Egg protein (most brands), formaldehyde (trace), polysorbate 80, gentamicin or neomycin (trace), thimerosal (multi-dose vials only)
Common Side Effects
Sore arm (~50%), fatigue (~10–15%), headache (~10%), muscle aches (~10%), low-grade fever (1–2%). FluMist: runny nose, congestion, mild sore throat.
Serious Adverse Events
Anaphylaxis ~1 per million. Guillain-Barré syndrome: ~1–2 additional cases per million doses (background rate ~10–20 per million/year). Flu illness itself raises GBS risk substantially more than the vaccine. Oculorespiratory syndrome rare and self-limited.
HPV (Gardasil 9)
Brand names: Gardasil 9
Prevents: 9 high-risk and wart-causing HPV types responsible for ~90% of cervical cancers, plus most anal, oropharyngeal, vulvar, vaginal, and penile cancers, and genital warts.
Ingredients
- Type
- Recombinant subunit (virus-like particles, yeast-grown)
- Adjuvant
- Amorphous aluminum hydroxyphosphate sulfate (~0.5 mg)
- Other
- Sodium chloride, L-histidine, polysorbate 80, sodium borate, yeast protein (residual)
Common Side Effects
Sore injection site (~85%), fainting in adolescents — sit or lie down for 15 minutes after vaccination, headache (~30%), fatigue (~25%), low-grade fever (~10%), nausea (~5%). Among the more reactogenic shots locally.
Serious Adverse Events
Anaphylaxis ~1.7 per million doses. No association with autoimmune disease, infertility, premature ovarian failure, or POTS confirmed in extensive post-licensure surveillance across hundreds of millions of doses globally.
Tdap — Adolescent/Adult
Brand names: Boostrix, Adacel
Prevents: Tetanus, diphtheria, pertussis booster. Recommended at age 11–12, in every pregnancy (27–36 weeks), and as a one-time substitute for a Td booster in adults.
Ingredients
- Type
- Toxoid (D, T) + acellular subunit (aP) — lower dose than DTaP
- Adjuvant
- Aluminum hydroxide or aluminum phosphate (~0.33 mg)
- Other
- Formaldehyde (trace), 2-phenoxyethanol, glutaraldehyde (trace)
Common Side Effects
Sore arm (~75%), headache (~40%), fatigue (~30%), muscle aches (~20%), low-grade fever (~5%), nausea/GI upset (~10–15%). Typically last 1–3 days.
Serious Adverse Events
Severe allergic reaction < 1 per million. Brachial neuritis (shoulder nerve inflammation) very rare. Arthus reaction (severe local reaction) rare — mainly in those who received tetanus boosters too frequently.
Meningococcal ACWY (MenACWY)
Brand names: Menactra, Menveo, MenQuadfi
Prevents: Neisseria meningitidis serogroups A, C, W, Y — bacterial meningitis and bloodstream infection; can be rapidly fatal.
Ingredients
- Type
- Conjugate
- Adjuvant
- None
- Other
- Sodium chloride, sodium phosphate, formaldehyde (trace, some brands), CRM197 or diphtheria toxoid carrier
Common Side Effects
Sore arm (~40%), headache (~30%), fatigue (~30%), muscle aches (~20%), irritability or low-grade fever in younger children.
Serious Adverse Events
Severe allergic reaction very rare. Small historical GBS signal with Menactra not seen with current products. No other established serious adverse events.
Meningococcal B (MenB)
Brand names: Bexsero, Trumenba; Penbraya (MenABCWY combo)
Prevents: Neisseria meningitidis serogroup B. Recommended via shared decision-making for ages 16–23.
Ingredients
- Type
- Recombinant subunit
- Adjuvant
- Aluminum hydroxide
- Other
- Sodium chloride, histidine, sucrose
Common Side Effects
Notably reactogenic: sore arm (~85%), fatigue (~50%), muscle pain (~50%), headache (~40%), chills (~25%), fever (~5–10%), nausea (~15%). Symptoms typically last 1–3 days.
Serious Adverse Events
Severe allergic reaction very rare. No other established serious adverse events in post-licensure data.
Shingrix (Recombinant Zoster Vaccine)
Brand names: Shingrix
Prevents: Shingles (herpes zoster) and postherpetic neuralgia. Recommended for immunocompetent adults 50+ and immunocompromised adults 19+. Two-dose series 2–6 months apart.
Ingredients
- Type
- Recombinant subunit (glycoprotein E)
- Adjuvant
- AS01B — combination of MPL + QS-21 saponin in liposomes. Potent adjuvant designed to overcome age-related immune decline.
- Other
- Sodium chloride, dipotassium phosphate, sucrose, polysorbate 80
Common Side Effects
Notably reactogenic. Sore arm (~78%), fatigue (~45%), muscle pain (~45%), headache (~38%), shivering (~27%), fever (~21%), GI symptoms (~17%). Typically 2–3 days. Many feel meaningfully unwell for a day — this is exactly what makes the vaccine work so well in aging immune systems.
Serious Adverse Events
Anaphylaxis very rare. Small post-licensure GBS signal (~3–6 additional cases per million doses in adults 65+); absolute risk very low and outweighed by shingles/PHN prevention benefit. No association with autoimmune flares in well-controlled studies.
Efficacy: 97% effective at preventing shingles in ages 50–69; 91% effective in 70+; protection lasting 7–10+ years.
Pneumococcal Adult (PCV15/20/21 + PPSV23)
Brand names: Vaxneuvance (PCV15), Prevnar 20, Capvaxive (PCV21), Pneumovax 23 (PPSV23)
Prevents: Pneumococcal pneumonia, meningitis, bacteremia. Recommended at 65+ and earlier for those with certain medical conditions.
Ingredients
- Type
- Conjugate (PCV) or polysaccharide (PPSV23)
- Adjuvant
- Aluminum phosphate in PCV; none in PPSV23
- Other
- Polysorbate 80, succinate buffer, sodium chloride, phenol (PPSV23)
Common Side Effects
Sore arm (~50–70%), muscle aches (~25%), fatigue (~20%), low-grade fever (~5%), headache. PPSV23 tends to cause more local reactions than PCV formulations.
Serious Adverse Events
Severe allergic reaction < 1 per million. No other established serious adverse events.
RSV Vaccines
Brand names: Arexvy (GSK), Abrysvo (Pfizer), mResvia (Moderna mRNA); Beyfortus (nirsevimab — monoclonal antibody for infants)
Prevents: RSV lower respiratory tract disease. Recommended for adults 75+, adults 60–74 at increased risk, and pregnant women at 32–36 weeks (Abrysvo) to protect newborns.
Ingredients
- Type
- Recombinant subunit (Arexvy, Abrysvo); mRNA (mResvia)
- Adjuvant
- Arexvy: AS01E. Abrysvo: none. mResvia: none
- Other
- Trehalose, polysorbate 80, sodium chloride, buffers; lipid nanoparticles (mResvia)
Common Side Effects
Sore arm (~60%), fatigue (~30%), muscle pain (~25%), headache (~25%), joint pain (~20%). Mild and self-limited in most.
Serious Adverse Events
Small post-licensure GBS signal under active investigation; absolute rate appears < 10 per million doses. Benefit-risk still favors vaccination in target groups (75+, high-risk 60–74, late pregnancy). Severe allergic reaction very rare.
COVID-19 (Current ACIP Recommendations)
Brand names: Pfizer-BioNTech (Comirnaty), Moderna (Spikevax), Novavax
Prevents: Severe disease, hospitalization, and death from SARS-CoV-2.
Ingredients
- Type
- mRNA (Pfizer, Moderna); recombinant protein subunit (Novavax)
- Adjuvant
- None for mRNA vaccines. Novavax uses Matrix-M (saponin-based)
- mRNA ingredients
- Lipid nanoparticles (including PEG-lipid), tromethamine, acetate buffer, sucrose, sodium chloride
- Novavax ingredients
- Sodium phosphate, sodium chloride, polysorbate 80, Matrix-M adjuvant
Common Side Effects
Sore arm (60–80%), fatigue (~50%), headache (~40%), muscle aches (~30%), chills (~20%), fever (~15% — more common after dose 2 of mRNA vaccines), joint pain, axillary lymph node swelling.
Serious Adverse Events
Anaphylaxis ~2–5 per million. Myocarditis/pericarditis after mRNA vaccines, mainly young males ages 12–29: ~10–40 per million — typically mild and self-limited; COVID infection itself carries meaningfully higher myocarditis risk. TTS was associated with the discontinued J&J adenoviral vector vaccine only; not associated with current mRNA or Novavax vaccines.
Td (Tetanus, Diphtheria Booster)
Brand names: Td booster — every 10 years
Prevents: Maintains protection against tetanus and diphtheria in adults.
Ingredients
- Type
- Toxoid
- Adjuvant
- Aluminum phosphate or aluminum hydroxide
- Other
- Formaldehyde (trace), sodium chloride, phosphate buffers
Common Side Effects
Sore arm (~60%), redness or swelling (~25%), fatigue; low-grade fever uncommon.
Serious Adverse Events
Severe allergic reaction very rare. Arthus reaction (severe local reaction) rare — mainly in those receiving tetanus boosters too frequently.
How to Interpret Adverse Event Data
Common Side Effects vs. Serious Adverse Events
Common side effects are expected immune-activation symptoms — sore arm, fatigue, low-grade fever, muscle aches. They reflect your immune system mounting a response, which is the point. Typically resolve in 1–3 days.
Serious adverse events are rare events that may require medical attention — anaphylaxis, seizures, neurological events. Reported as rates per million doses, tracked through the active VSD (real medical records from millions of patients) and passive VAERS (intentionally over-inclusive for signal detection).
Background Incidence Matters
If a condition occurs at 100 cases per million per year at baseline, and you see 100 cases per million after vaccination, that's coincidence — not a vaccine signal. Real safety signals emerge when the post-vaccination rate meaningfully exceeds the expected background rate. VAERS reports alone don't establish causation; controlled comparison to background rates is required.
VAERS: Signal Detection Tool, Not a Measurement Tool
VAERS accepts reports from anyone and is intentionally over-inclusive — to catch rare safety signals early. Death reports in VAERS include people who died of unrelated causes hours, days, or weeks after vaccination. When a VAERS pattern looks concerning, it's investigated through controlled studies and the active VSD. Raw VAERS numbers cited as vaccine-caused harms is a systematic misuse of the database.
Comparing Risk: Vaccine vs. Disease
| Event | Risk from Vaccine | Risk from Disease |
|---|---|---|
| Encephalitis (MMR vs. measles) | < 1 per million doses | ~1 per 1,000 measles cases |
| Guillain-Barré (flu vaccine vs. flu illness) | ~1–2 additional per million | Several-fold higher with flu illness |
| Myocarditis (mRNA COVID vs. COVID infection) | 10–40 per million young males | Higher with COVID infection itself |
| Intussusception (rotavirus vs. pre-vaccine) | 1–5 per 100,000 | 55,000–70,000 US infant hospitalizations/year |
| Cervical cancer (HPV vaccine) | No documented serious signal | ~36,000 HPV-attributable US cancers/year |
Claims Ruled Out by Large-Scale Evidence
- ·Vaccines causing autism (MMR specifically, thimerosal specifically, total vaccine load — studied in cohorts of millions, consistently disproved)
- ·HPV vaccine causing infertility, premature ovarian failure, or POTS
- ·Aluminum adjuvants causing Alzheimer's disease
- ·"Too many vaccines too soon" overwhelming infant immune systems (immune response capacity is orders of magnitude greater than the schedule's antigenic load)
Well-Characterized Real Risks
- ·Anaphylaxis to any vaccine: ~1 per million doses
- ·Myocarditis after mRNA COVID vaccines in young males: ~10–40 per million; typically mild; lower than COVID infection itself
- ·Intussusception after rotavirus: ~1–5 per 100,000
- ·Febrile seizures after MMR or MMRV: ~1 per several thousand; no long-term harm
- ·Guillain-Barré syndrome after some vaccines: ~1–5 additional per million; typically reversible
Sources & Where to Verify
Every claim in this reference can be verified against the primary sources below. When researching a specific vaccine, start with the package insert — Section 11 lists all ingredients; Section 6 lists adverse reactions with rates from clinical trials.
Primary Regulatory & Surveillance Sources
Final Note
Vaccine science is one of the most heavily studied areas of medicine, with post-licensure surveillance running continuously across multiple national systems. That doesn't mean every product is perfect or that legitimate questions don't exist — they do, and they're how the field improves (whole-cell pertussis replaced by acellular, Zostavax replaced by Shingrix, ongoing mRNA platform refinements). Healthy skepticism is appropriate. The standard for informed consent is engaging with the actual evidence — which is what this reference is meant to support.
Compiled by Natalie Elie, CFWHE · NEwellness101 · For educational and clinical reference use.