New information from the United States Food and Drug Administration announced Thursday that the flu vaccine this year has a 36 percent efficiency rate overall. Thousands of people have died from the flu so far this year, including 84 children across the United States, Puerto Rico, Guam and the U.S. Virgin Islands.

While 36 percent effective may seem like a low level of efficiency, it’s important to note that the number pertains to how effective the vaccine is in protecting against several types of the flu.

How many types of influenza are there?

There are four types of influenza, all classified into either A, B, C or D categories. Usually, the versions of the virus that humans get each season are either type A or B, according to the Centers for Disease Control. The most common type A influenza viruses circulating among humans right now are H1N1 and H3N2, the types of influenza B that are circulating are B/Yamagata and B/Victoria. While there are numerous strains and types of the flu, these are the ones to worry about this season.

How effective is the flu vaccine?

The vaccine has an overall effectiveness of 36 percent. But that number is an average of the effectiveness of the vaccine between the several most popular strains of the virus. The vaccine was shown to be about 25 percent effective against the H3N2 virus this season, according to CDC Acting Director Dr. Anne Schuchat. But the vaccine it 67 percent effective against the H1N1 and 42 percent effective against the B categories of the virus.

For children between the ages of six months and eight years old, the vaccine is even more effective. While the numbers might seem low, the vaccine does prevent some people from getting sick, and from passing the virus on to others.

As the deadly flu season continues the CDC has recommended that people who still don’t have a flu shot get one. Just last week, officials with the Centers for Disease Control said that there is no way to know when the flu season would end. Acting Director Dr. Anne Schuchat said “If we stay vigilant and take steps to fight flu we can reduce the risk of getting - and transmitting - it.”

flu graph week 5 The flu has reached infection levels that rival the year of swine flu, according to the CDC. Photo: Centers for Disease Control