The World Health Organization (WHO) coordinates the contents of the vaccine each year to contain the most likely strains of the virus to attack the next year. "The WHO Global Influenza Surveillance Network was established in 1952 [renamed "Global Influenza Surveillance and Response System" in 2011]. The network comprises four WHO Collaborating Centres (WHO CCs) and 112 institutions in 83 countries, which are recognized by WHO as WHO National Influenza Centres (NICs). These NICs collect specimens in their country, perform primary virus isolation and preliminary antigenic characterization. They ship newly isolated strains to WHO CCs for high level antigenic and genetic analysis, the result of which forms the basis for WHO recommendations on the composition of influenza vaccine for the Northern and Southern Hemisphere each year. "The Global Influenza Surveillance and Response Systems selection of viruses for the vaccine manufacturing process is based on its best estimate of which strains will predominate the next year, amounting in the end to well-informed but fallible guesswork.Formal WHO recommendations were first issued in 1973. Beginning in 1999 there have been two recommendations per year: one for the northern hemisphere and the other for the southern hemisphere.Historical annual reformulations of the influenza vaccine are listed in a separate article.
Lustra may refer to:

Lustrum (plural "Lustra"), a period of five years. Lustra, poetry, by Ezra Pound. Lustra, Campania, a commune in the province of Salerno (Campania, Italy). Lustra (album), a 1997 album by British band Echobelly. Lustra (band), a pop punk band best known for the song "Scotty Doesnt Know" in the movie EuroTrip