What Type of Vaccine is the Flu Vaccine?

The flu is a nuisance during winter, spreading quickly and putting most people out of work or school for a couple of days as the disease runs its course. In some cases however, the flu vaccine poses a more serious problem. High-risk groups including the elderly, immunocompromised, and people with chronic diseases are especially vulnerable to this otherwise relatively harmless disease. People categorised as high-risk are susceptible to complications like pneumonia and bronchitis amongst others. Because of this vulnerability, the seasonal flu vaccine is an important preventative measure that protects at-risk populations from a serious illness. This article looks at the ins and outs of the seasonal flu vaccine.

An introduction to flu and the flu vaccine

The flu is caused by the influenza virus, of which there are three distinct classes. Type A is the most serious type of infection, made more dangerous by the fact that Type A viruses are constantly changing, meaning that they can easily bypass our immune system even if we have prior immunity against the flu. Swine flu (medically known as the H1N1 virus) is a good example of a modern Type A virus, and historically Type As have been responsible for global pandemics.

Type B infections cause small scale outbreaks and milder illness, mostly affecting younger children whose immune system hasn’t had a chance to experience a broad range of different viruses and develop a resistance against them. Finally Type C infections are extremely mild and easily confused with the common cold as symptoms are not serious and pass quickly.

Every year a new seasonal flu jab needs to be developed as the major concerns are Type A and Type B infections. Type A viruses are constantly changing, as mentioned above, which is why a new vaccine needs to be formulated every year to keep us immune.

How are new vaccines formulated?

The World Health Organisation, often abbreviated to WHO, is responsible for examining the flu viruses that might pose a risk every season. This assessment is made as early as February, and gives companies and healthcare services enough time to prepare vaccines for the coming season (the flu season is thought to begin at around October, just as winter sets in).

After a comprehensive study of flu strains, three are selected based on the dangers they pose, and these are included in the yearly vaccine. The WHO recommended vaccine is manufactured and distributed across this part of the world, not just in the UK. Vaccine production begins around March and by September there are enough doses ready for circulation.

How are new flu vaccines made?

After the WHO has made its recommendation, vaccine manufacturers begin the process of generating the vaccine for widespread use. The seasonal jab will usually contain three strains, two of which will be Type As while the last will be a Type B.

The necessary strains of vaccine are incubated (grown under special conditions) in chicken eggs before being killed and treated to make a safe and effective vaccine.

How do flu vaccines work?

Because the viruses are killed after being grown, the vaccination is known as an inactivated or killed vaccine. What this means is that the dead virus is introduced to the body to cause an immune response. Your body produces a special class of immune compounds called antibodies which are specific to the strains of virus you encounter. Once these antibodies have been produced in response to the vaccination, they will remain in your bloodstream ready to deal with any future encounters with the actual virus.

Typically speaking you will be immune to the flu within 14 days of vaccination, however because of the fact that the vaccine induces antibody mediated immunity, this immunity will fade over the time, hence the need for a booster injection later in the year.

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