Glossary of Terms

Common terms that you may encounter on the site.


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A (9) | B (2) | C (2) | D (2) | E (6) | G (1) | H (2) | I (8) | K (1) | L (1) | M (2) | P (5) | R (1) | S (5) | T (4) | U (1) | V (6)

  • Thimerosal

    An ethylmercury compound used as a preservative. Thimerosal was used in many killed-virus vaccines until it was recommended to be removed from most childhood vaccines in 1999. It is still used in multi-dose influenza vaccines, and can be found trace amounts (a relic of the manufacturing process) in some other vaccines.

  • Tissue culture (cell culture)

    A collection of living cells that provides a cultivation medium for viruses, bacteria, and other organisms. The propagation of viruses in tissue culture was an important milestone in studying viruses and creating vaccines. The team of John Enders, Thomas Weller, and Frederick Robbins won a Nobel Prize in 1954 for developing tissue culture techniques in their study of poliovirus. Tissue culture is often used interchangeably with cell culture, though it can refer to the use of pieces of tissue, rather than collections of cells, as a growth medium.

  • Toxin

    Poisonous substance capable of causing disease. Toxins are generated by cells or organisms; toxins generated by bacteria are often the actual cause of the disease associated with those particular bacteria. Tetanus, for example, is not directly caused by the presence of Clostridium tetani bacteria, but by tetanospasmin, the toxin they produce.

  • Toxoid

    A toxin modified to invoke an antibody response, but not capable of causing disease. Immunizations for diphtheria and tetanus use toxoids.