Does this mean that Sanofi Pasteurs flu vaccine is contaminated?
No. The sterility problems occurred in monovalent concentrates, not in the final vaccine product. The failed monovalents represented a small number of the total number of monovalents produced and were rejected by the firm and not used for further processing. Each year, influenza virus vaccine represents a “new” product, with at least one of the strains from the previous year changed based on global epidemiological information. Three strains are used in each year’s vaccine. Monovalent concentrates are intermediates that are used to formulate the trivalent vaccine. Generally, influenza vaccine manufacturers produce monovalents of each strain throughout the winter and spring months, then begin trivalent formulation and filling of final vaccine product in the early summer.
