Thermolabile means a product whose structure breaks down with heat: outside its band the active substance degrades, protein folding is disturbed or a suspension separates. Vaccines are the best-known members of the group.
The damage is usually invisible, excursions add up, and it cannot be undone. Because degradation speeds up exponentially with temperature, a few degrees shorten shelf life noticeably. Freezing is a separate danger: WHO places liquid aluminium-adjuvanted vaccines such as hepatitis B in the freeze-sensitive group.
Section 10.4 of the TİTCK Good Distribution Practice Guide sets these requirements for transporting temperature-sensitive products:
- qualified thermal packaging, temperature-controlled containers or vehicles,
- ice packs placed so they do not touch the product,
- a check that stops partly frozen ice packs being used by mistake,
- physical separation between frozen and chilled ice packs.
In storage, the same guide requires monitoring devices and alarms at the worst-case points of a 2-8 °C cold room (Section 4.2.5). After an excursion, the decision to use or destroy the product is made from the temperature record it has built up since manufacture.