In the US swine flu scare of 1976, President Gerald Ford was confronted with a potential swine flu pandemic. The vaccination program was rushed, yet plagued by delays and public relations problems. Meanwhile, maximum military containment efforts succeeded unexpectedly in confining the new strain to the single army base where it had originated. On that base, a number of soldiers fell severely ill, but only one died. The program was canceled after about 24% of the population had received vaccinations. An excess in deaths of 25 over normal annual levels as well as 400 excess hospitalizations, both from Guillain–Barré syndrome, were estimated to have occurred from the vaccination program itself, demonstrating that the vaccine itself is not free of risks. The result can be cited to support lingering doubts about vaccination as well as to counter ungrounded claims about the safety of vaccination. In the end, however, even the maligned 1976 vaccine may have saved lives. A 2010 study found a significantly enhanced immune response against the 2009 pandemic H1N1 in study participants who had received vaccination against the swine flu in 1976. Quadrivalent vaccines for seasonal flu
A quadrivalent flu vaccine administered by nasal mist was approved by the FDA in March 2012. Fluarix Quadrivalent was approved by the FDA in December 2012.In 2014, the Canadian National Advisory Committee on Immunization (NACI) published a review of quadrivalent influenza vaccines.Starting with the 2018–2019 influenza season most of the regular-dose egg-based flu shots and all the recombinant and cell-grown flu vaccines in the United States are quadrivalent.
Notes
See also
H5N1 vaccine
Seasonal influenza vaccine brands
Universal influenza vaccine

References
Further reading
World Health Organization (October 2017). The immunological basis for immunization series: module 23: influenza vaccines. World Health Organization (WHO). hdl:10665/259211. ISBN 978-9241513050. Ramsay M (ed.). "Chapter 19: Influenza". Immunisation against infectious disease. Public Health England. Hamborsky J, Kroger A, Wolfe S, eds. (2015). "Chapter 12: Influenza". Epidemiology and Prevention of Vaccine-Preventable Diseases (13th ed.). Washington D.C.: U.S. Centers for Disease Control and Prevention (CDC). ISBN 978-0990449119. Budd A, Blanton L, Grohskopf L, Campbell A, Dugan V, Wentworth DE,  et al. (March 29, 2019). "Chapter 6: Influenza". In Roush SW, Baldy LM, Hall MA (eds.). Manual for the surveillance of vaccine-preventable diseases. Atlanta GA: U.S. Centers for Disease Control and Prevention (CDC). National Advisory Committee on Immunization (May 2020). "Canadian Immunization Guide Chapter on Influenza and Statement on Seasonal Influenza Vaccine for 2020–2021" (PDF). Public Health Agency of Canada. Cat. : HP37-25F-PDF; Pub. : 200003. Lay summary. {{cite web}}: Cite uses deprecated parameter |lay-url= (help)
National Advisory Committee on Immunization (NACI) (May 2018). NACI literature review on the comparative effectiveness and immunogenicity of subunit and split virus inactivated influenza vaccines in adults 65 years of age and older (PDF). Government of Canada. ISBN 9780660264387. Cat. : HP40-213/2018E-PDF; Pub. : 180039. Lay summary. {{cite book}}: Cite uses deprecated parameter |lay-url= (help)
Rajaram S, Wojcik R, Moore C, Ortiz de Lejarazu R, de Lusignan S, Montomoli E,  et al. (August 2020). "The impact of candidate influenza virus and egg-based manufacture on vaccine effectiveness: Literature review and expert consensus". Vaccine.