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.
Other quadrivalent flu shots are approved for people 3 years and older. The quadrivalent nasal spray vaccine is approved for people 2 through 49 years of age who do not have contraindications to the nasal spray vaccine. Refer to the table of 2015-16 approved influenza vaccines in the U.S. for more information.