Atlanta, GA—As many as 151 to 166 million doses of injectable influenza vaccine are projected to be available for the 2017–2018 season, according to estimates from manufacturers, with most of those, 119 million, being quadrivalent vaccines.

The CDC reports that 73 million doses already had been distributed as of mid-September.

“Optimally, vaccination should occur before the onset of influenza activity in the community. If possible, vaccination should be offered by the end of October and should continue to be offered as long as influenza viruses are circulating and unexpired vaccine is available,” CDC researchers advise in a review in the Morbidity & Mortality Weekly Report, which also heralded some possible changes in vaccine manufacturing in the future.

Public-health officials point out that, between May 21 and September 23, 2017, influenza A(H3N2), influenza A(H1N1)pdm09, and influenza B viruses cocirculated worldwide, with influenza B viruses predominating from late May through late June in the United States, although influenza A viruses were most commonly reported beginning in early July. 

Beginning at that point, influenza A(H3N2) viruses also predominated in many countries in the Southern Hemisphere, the CDC reports. The researchers also note that influenza B viruses can show up any time during the flu season, but they tend to circulate later and frequently create a second peak of influenza activity in the late winter and spring in the United States and other countries in the Northern Hemisphere.

The article also discussed an important innovation in flu vaccine development. With the exceptions of RIV3, RIV4, and ccIIV4, all currently available vaccines use embryonated eggs to propagate viruses. 

“Egg propagation of influenza A(H3N2) viruses often leads to genetic changes that have antigenic implications,” researchers point out, adding that, for the vaccine ccIIV4, the influenza A(H3N2) virus component will be cell-derived for the first time.

“This represents a first step toward producing a totally egg-independent inactivated virus vaccine,” the study authors explain. “Recombinant technology is used in the production of RIV3 and RIV4; therefore, they are manufactured without the use of influenza viruses or eggs. The use of egg-independent vaccine technologies is likely to provide vaccines that more precisely represent the antigenic characteristics of circulating viruses and have the potential to offer improved protection.”

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