Influenza or “flu” is a respiratory disorder caused by the virus strains influenza A or influenza B. Influenza is a commonly occurring disorder and is contagious too, where it affects the upper or the lower respiratory tract. It commonly occurs in the winter months and in the early spring season.


Flu symptoms are similar to those of a common cold, but are more severe. The symptoms include chest congestion, coughing, body ache as well as headaches, fever, and weakness. In certain cases when influenza becomes severe, it results in pneumonia, which can be a life-threatening disorder.


Prevention is the best way to avoid a bout of flu, and vaccines are available against the influenza viruses.


Flu vaccine

The traditional flu vaccine is a trivalent or quadrivalent alternative that is effective against three or four virus strains that cause influenza. It is an inactivated vaccine and is called trivalent when it has three components and quadrivalent when it has four components. The flu vaccine is usually administered via injection into the muscle, but a nasal spray variant, which was not recommended in the flu season of 2016 and 2017, is also available. An intradermally administered shot, recommended for those between the ages of 18 and 64, is also available.


It is recommended that the flu vaccine be given every year ahead of the flu season. The vaccine must definitely be given to—

  • Adults who are 65 years and older
  • Children who are aged 6 months to 5 years
  • Women who are pregnant
  • Those suffering from health conditions
  • People of Alaskan Native and Native American ethnic groups
  • People who are staying in nursing homes or are in long-term care facilities
  • Those who travel often, especially abroad


Those who must not be administered the flu shot include

  • Children who are under the age of 6 months
  • Individuals who are allergic to ingredients present in the flu vaccine such as eggs, or those who are allergic to the vaccine itself

Those with symptoms of Guillain-Barré syndrome and those feeling unwell must also not take the flu shot without consulting a doctor.


Flu HD vaccine

Fluzone HD or Fluzone high dose is the inactivated influenza vaccine recommended for those who are aged 65 years and over. Fluzone HD also comes in an injectable formulation and is made up of three strains of the flu virus.


This vaccine, however, differs from the regular flu vaccine in that the antigen present against the flu virus is found to be four times greater in quantity than that present in the regular flu vaccine. The antigen is present in four times greater strength because senior citizens produce antibodies that protect the body at a 50 to 75 percent lower level compared to young adults. Studies revealed that a higher dose of antigens produced more antibodies in older adults, thus compensating for the lower count and providing protection against the influenza viruses. Statistics also revealed a 25 percent drop in the occurrence of flu in those older adults receiving a higher-dose flu vaccine.