Argumentum ad sarcina inserta

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Argumentum ad sarcina inserta is a fallacious anti-vaccination argument that holds that the contents of the warnings on package inserts of vaccines and diagnostic tests indicates that the vaccine is very dangerous or that the diagnostic test has a high failure rate.

These arguments fail to take into account the actual measured rates of adverse reactions or actual measured false positive rates, or to take into account the proven beneficial effect of vaccination.

If you're curious, The CDC has is an official list of all known vaccine ingredients.[1]

Basic format[edit]

P1: Package insert X says medicine Y contains ingredient Z.
P2: Ingredient Z is poisonous.
C: Therefore, medicine Y is poisonous.

The above argument, which is what most anti-med cranks default to, conveniently ignores the idea that certain qualities of an element can be cancelled out by another element. This is why sodium chloride (table salt) is safe to ingest, while chlorine gas is not. Importantly, the argument also ignores the fact that virtually everything is poisonous at some dose level (the dose makes the poison), so yes people have died from ingesting too much salt,[2] but not at anywhere near the levels that occur in vaccines.

Another common argument can be:

P1: Doctor A wants to give patient B medicine C. Patient B asks if doctor A if they have read the package insert for medicine C.
P2: Doctor A says he has not read the full package insert for medicine C.
C: Therefore, doctor A is an idiot for unquestioningly prescribing medicine C.

This argument also conveniently ignores the fact that doctors do read package inserts, as some patients may be allergic to certain ingredients within the medicine.


  • The package insert on the HIV test says that the test can give false positives if you are also taking a pregnancy test. Therefore the HIV test is useless.
  • My doctor told me to take (insert prescription medicine here), but he hasn't even read the package insert for the medicine. Therefore, he is a shill for Big Pharma.

See also[edit]