About this guide
Definitions: how "vaccine" was defined, then and now
| Who / term | Before | After | When |
|---|---|---|---|
| CDC Vaccine | A product that stimulates a person's immune system to produce immunity to a specific disease, protecting the person from that disease. archived copy | A preparation that is used to stimulate the body's immune response against diseases. archived copy | Changed between 1 and 28 September 2021 (Wayback snapshots) |
| CDC Vaccination | The act of introducing a vaccine into the body to produce immunity to a specific disease. archived copy | The act of introducing a vaccine into the body to produce protection from a specific disease. archived copy | Changed between 1 and 28 September 2021 |
| Merriam-Webster Vaccine | a preparation of killed microorganisms, living attenuated organisms, or living fully virulent organisms that is administered to produce or artificially increase immunity to a particular disease archived copy | a preparation that is administered (as by injection) to stimulate the body's immune response against a specific infectious agent or disease: such as a: an antigenic preparation of a typically inactivated or attenuated ... pathogenic agent ... or one of its components or products ... b: a preparation of genetic material (such as a strand of synthesized messenger RNA) that is used by the cells of the body to produce an antigenic substance (such as a fragment of virus spike protein) archived copy | Changed between 15 and 26 January 2021 (Wayback snapshots) |
Disease doses (this guide's counting term): each dose of a vaccine counts once for every disease it covers. A 6-in-1 (DTaP/IPV/Hib/HepB) counts as 6, MMRV as 4, the pre-school 4-in-1 (dTaP/IPV) as 4, MMR, DTaP and the teenage 3-in-1 (Td/IPV) as 3, Hib/MenC as 2, and a single-disease vaccine as 1. All meningococcal groups count as one disease, so MenACWY counts as 1. Injections are the number of shots. Products given counts each combination once. Used in How the schedule has changed.
Terms used in the injury, SIDS and retraction sections
- VAERS
- Vaccine Adverse Event Reporting System, run by CDC and FDA. Anyone can report a health problem after a vaccine. A report does not show the vaccine caused it.
- Serious report
- In VAERS, a report of death, a life-threatening illness, a hospital stay or a longer stay, permanent disability, or a birth defect.
- VICP / VDPS
- The US Vaccine Injury Compensation Program and the UK Vaccine Damage Payment Scheme, which pay people found (or agreed in a settlement, in the US) to have been harmed by a vaccine.
- SIDS, SUID and unascertained
- SIDS: the sudden death of a baby under 1 that stays unexplained after a full investigation. SUID (US) adds deaths of unknown cause and accidental suffocation in bed. "Unascertained" (England and Wales) means the cause could not be found.
- Self-controlled study
- A study that compares the same child's risk in the days just after a vaccine with that child's risk at other times, so the child is their own comparison.
- Crude incidence
- Cases in a year divided by the whole population, with no adjustment for age or vaccination.
- Retracted, withdrawn, removed
- Retracted: the journal publishes a notice that the paper should no longer be relied on, but the paper stays visible, marked. Withdrawn: usually an accepted paper taken down before final publication. Removed: taken off the site, sometimes with no notice.
With thanks
I didn't do the real work behind a lot of what is on this page. These people did. They went through the courts and did it properly. If you want to know more, please watch them, listen to them and follow them, not me. All I've done is point at the information in a way I understand. Their views and claims are their own; this guide only says who they are and where to find them.
- ICAN (Informed Consent Action Network): a non-profit, founded in 2016 and based in Austin, Texas.
- Del Bigtree: founder of ICAN and host of The HighWire.
- Aaron Siri: managing partner of Siri & Glimstad LLP, a law firm that regularly represents ICAN.
- Toby Rogers: has a PhD in political economy from the University of Sydney and writes the uTobian newsletter on Substack.
Thank you too to all the scientists running these trials and studies, and to everyone helping them and taking part in them.
About this data
- Every figure links to its source. Most are official government health agencies (UKHSA/NHS, CDC), medicine regulators (EMA, MHRA via emc, FDA) or major peer-reviewed studies.
- Counts are reported cases unless marked 'estimated'. UK figures are often England-only.
- 'Share of cases that were unvaccinated' is not the same as risk; it depends on how many people in the population are vaccinated.
- Pre-vaccine figures come from older reporting systems and are not exactly comparable with modern surveillance.
- Items marked GAP or UNVERIFIED need checking before publication.
- This page gives no advice and takes no position. For decisions about your own family, read the linked documents and speak to a clinician you trust.
- Compiled 2026-10-22. Figures change; check the linked source for the latest version.