The term "cold adapted" means that an organism or virus has evolved or been developed to function optimally at lower temperatures than normal body temperature. In the context of viruses like the live attenuated influenza vaccine (LAIV), cold adapted means the virus can replicate well at the cooler temperatures found in the nose (nasal mucosa) but not at the warmer core body temperature. This allows the vaccine virus to stimulate immune responses in the nasal passages without causing infection deeper in the warmer parts of the body like the lungs. For organisms, cold adaptation refers to physiological changes that enable survival and function in cold environments. Specifically for the live attenuated influenza vaccine, the cold adapted virus replicates effectively at around 33°C in the nose but cannot replicate well at 37°C or higher in the lungs, which enhances safety while inducing local immunity.
For general biological cold adaptation, it means developing mechanisms such as increased heat production or insulation to survive and function in cold climates or conditions.
In summary, cold adapted means optimized for lower temperature environments or conditions, either naturally through evolution or artificially through laboratory development in the case of vaccines.
