A federal advisory panel has chosen the influenza virus strains to be used in vaccine production for the 2016-17 flu season, alleviating some concerns about a possible supply shortage because of potential manufacturing delays.
The U.S. Food and Drug Administration's advisory committee recommended the California variant for the H1N1 and Hong Kong variations of the H3N2 strains of the influenza virus. It chose the Brisbane variation of influenza B to comprise the strains for the trivalent vaccine, and recommended adding the Phuket variant of the influenza B strain for the quadrivalent vaccine.
The decision comes as a relief to vaccine manufacturers, many of whom began production of next season's flu vaccine in January based on the World Health Organization's expected recommendations. Some feared a different decision by the advisory panel would mean vaccine companies would have to restart production from scratch. That would raise the possibility that much of the nation's supply would not be available by late August and early September, a time traditionally regarded as the start of the flu season.
Selecting flu strains for vaccines to be used in a season that is still months away requires regulators to review year-round surveillance data from 142 national influenza centers based in more than 100 countries. The data allow researchers to predict the strains they believe will be the most widespread. But there's always a chance they could be wrong.
Such was the case during the 2014-15 flu season when a mutation of the H3N2 virus caused that year's vaccine to have an efficacy rate of 23%, which led to some of the highest hospitalization rates among the senior population ever recorded. This season's flu vaccine was around 59% effective.
The challenge lies in the flu vaccine's production process. It can take at least six months to manufacture the majority of the vaccine supply. Around 90% of vaccines use a method that involves growing virus strains in eggs, a process used for more than seven decades.
The method, though reliable, does not allow for sudden changes, such as those that occurred in the 2014-15 flu season when the strain mutation surfaced three months into the vaccine production process, making it impossible for manufacturers to change course.
There is always a chance the FDA could still decide not to follow the advisory committee's recommendations, but it typically does so.