An antifreeze is an additive which lowers the freezing point of a water-based liquid. An antifreeze mixture is used to achieve freezing-point depression for cold environments and also achieves boiling-point elevation (anti-boil) to allow higher coolant temperature.
The strains of virus the trivalent vaccine protects against two A viruses (an H1N1 and an H3N2) and an influenza B virus. The quadrivalent vaccine adds another B virus to the vaccine which helps expand the level of protection to the recipient.
Some seasonal flu vaccines will be formulated to protect against three flu viruses (trivalent flu vaccines). All nasal spray vaccines are now quadrivalent; however, this makes up only a small portion of total vaccine availability.