The [[flu]] vaccine is an example of modern vaccination. Due to [[genetic]] changes in the influenza virus, new influenza vaccines are created each year. In some years the vaccines are less effective than in other years. According to the CDC,"Influenza viruses are always changing. Therefore, influenza vaccines are updated every year, and annual vaccination is recommended".<ref> "Inactivated Influenza Vaccine, What you need to know," a publication of the Center for Disease Control, 2006. Available online at: https://www.cdc.gov/nip/publications/VIS/vis-flu.pdf</ref> | The [[flu]] vaccine is an example of modern vaccination. Due to [[genetic]] changes in the influenza virus, new influenza vaccines are created each year. In some years the vaccines are less effective than in other years. According to the CDC,"Influenza viruses are always changing. Therefore, influenza vaccines are updated every year, and annual vaccination is recommended".<ref> "Inactivated Influenza Vaccine, What you need to know," a publication of the Center for Disease Control, 2006. Available online at: https://www.cdc.gov/nip/publications/VIS/vis-flu.pdf</ref> |