been weakened or killed and the viral antigen is purified and placed inside vials, syringes, or nasal sprayers. Done on a large-scale, this method is used to produce the flu vaccine for the human population. Other methods of manufacture Methods of vaccine generation that bypass the need for eggs include the construction of influenza virus-like particles (VLP). VLP resemble viruses, but there is no need for inactivation, as they do not include viral coding elements, but merely present antigens in a similar manner to a virion. Some methods of producing VLP include cultures of Spodoptera frugiperda Sf9 insect cells and plant-based vaccine production (e.g., production in Nicotiana benthamiana). There is evidence that some VLPs elicit antibodies that recognize a broader panel of antigenically distinct viral isolates compared to other vaccines in the hemagglutination-inhibition assay (HIA). A gene-based DNA vaccine, used to prime the immune system after boosting with an inactivated H5N1 vaccine, underwent clinical trials in 2011. On November 20, 2012, Novartis received FDA approval for the first cell-culture vaccine. In 2013, the recombinant influenza vaccine, Flublok, was approved for use in the United States. On September 17, 2020, the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) adopted a positive opinion, recommending the granting of a marketing authorization for Supemtek, a quadrivalent influenza vaccine (recombinant, prepared in cell culture). The applicant for this medicinal product is Sanofi Pasteur. Supemtek was approved for medical use in the European Union in November 2020. Australia authorised its first and cell-based vaccine in March 2021, based on an "eternal cell line" of a dog kidney. Because of the way it is produced, it produces better-matched vaccine (to the flu strains). Vaccine manufacturing countries According to the WHO, , countries where influenza vaccine is produced include: In addition, Kazakhstan, Serbia and Thailand had facilities in final stages of establishing production. Cost-effectiveness The cost-effectiveness of seasonal influenza vaccination has been widely evaluated for different groups and in different settings. In the elderly (over 65), the majority of published studies have found that vaccination is cost saving, with the cost savings associated with influenza vaccination (e.g. prevented health care visits) outweighing the cost of vaccination. In older adults (aged 50–64 years), several published studies have found that influenza vaccination is likely to be cost-effective, however the results of these studies were often found to be dependent on key assumptions used