Predicting Flu Virus Strains

The flu vaccine is produced every year in part by guessing and partly by science.

Professionals in the field meet under the auspices of the FDA on a yearly basis to try and predict which flu virus strains are most likely to spread across the U.S. in next yearly flu season.

They start by using samples from the Far East, where yearly flu strains typically start.

The flu vaccine contains three separate flu strains and is therefore referred to as a trivalent vaccine.

Most years experts manage to match their vaccine design in the spring to the strains that actually circulate throughout the country later in the year.

But this year, they had problems finding samples and being able to grow a strain referred to as the H3N2.

This year, the particular H3N2 strain that was left out of the vaccine wound up being the dominant influenza A virus which has accounted for more than 60% of flu cases.

Influenza A typically makes up about 85% of all flu cases and this year, it simply missed the boat.

A government scientific advisory board is now recommending for the first time a complete overhaul of the makeup of the flu vaccine for next year.

This move would replace all three flu virus strains in this year's vaccine with three new strains for next year.

This change could potentially cause delays for next year as vaccine makers grow the new strains and produce new flu shots.

Even though this year’s flu shot wasn’t all that helpful, it is still recommended yearly, especially for the very young, the very old and those with chronic illnesses.