For more than 30 years, the only option for the flu vaccine has been trivalent; that is, designed to protect against three strains of the influenza virus. Last year, for the first time, a new quadrivalent vaccine was introduced that provides protection against four varieties of the virus. This year will be the first time the quad vaccine is widely available, with the option to get it in the form of either a traditional shot or a nasal spray. 
The quadrivalent flu vaccine marks an advancement in our ability to fight the influenza virus. The trivalent version (still available this year) protects against two A viruses and two B viruses; the quad vaccine boosts the protection to two B viruses. With the trivalent vaccine, developers had to choose which B virus to include, even though there are two distinct B virus families that can vary widely and spread in most seasons. Instead of having to guess which one will cause the most issues that year, experts can now include both B viruses. A CDC model estimates this addition could prevent as many as 485 deaths a year.
The CDC and most experts don't specifically recommend the quadrivalent vaccine over the trivalent version, with most doctors simply specifying that their patients just need to get some form of the vaccine. Type B influenza does tend to strike children more than adults, however, and the quad vaccine would be a great option for seniors as they tend to be more susceptible to the flu in general. The standard-dose quadrivalent nasal spray is approved for healthy people 2 through 49 years of age and is a more popular option for children. The nasal spray is not recommended for pregnant women, who should seek the traditional shot instead.
As far as when you should seek out the quadrivalent vaccine, most experts recommend that you receive the flu shot by early fall. It takes about two weeks for the protection to kick in, and flu season typically begins as early as October in the U.S. and continues as late as May. The biggest peak is most commonly in January or February, but you should get the shot as early as you can to ensure the highest level of protection. We will be providing the quadrivalent vaccine as an option for our on-site flu clinics, but suggest to book early if you're interested to ensure your supply is reserved for your event.
The quadrivalent vaccine is more expensive that the traditional trivalent version, but does provide an extra level of protection.
Will you seek out the quadrivalent vaccine for yourself and/or your staff? Comment below with your thoughts. 
