Tuesday, December 7, 2021
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How is the flu shot made?

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Each year, the flu vaccination campaign begins in the fall. Recommended for populations at risk to avoid serious complications that can lead to death, this vaccine is often debated. What’s in it? How is it made? And under what conditions? We went to a production site to find out more.

How is the flu shot made? 

The annual flu vaccination campaign will take place in the fall of each year. the vaccine policy for this virus is to avoid complications, hospitalizations and deaths associated with severe influenza cases.

Therefore, vaccination influenza is fully supported and recommended for:

  • People who are considered to be at risk of severe influenza or complications (eg people aged 65 and over);
  • Or for people in regular contact with them (for example health professionals).

But vaccination is arousing more and more scepticism and in particular that against influenza given the variability in its effectiveness from one year to another. 

The viral composition changes every year

The manufacture of the influenza vaccine is a real race against time“, explains an industrial operations director of the Sanofi Pasteur sites in France. “Its main composition is made of 4 active ingredients called antigens, obtained from inactivated strains of the virus“.

The goal is to confront the immune system with a weakened form of the virus to teach it to recognize it and defend itself when the time comes. “Each year, production is launched in February, once the World Health Organization (WHO) sends us its recommendation for the selection of strains to put in the vaccine.”

The peculiarity of the flu vaccine is that every year its viral composition changes. The influenza virus is constantly evolving. These are not the same strains that circulate depending on the hemispheres and from year to year.

In all, since 1989, 43 different vaccine strains have been recorded in the northern hemisphere, including 29 changes in strain A and 14 changes in strain B, according to the WHO.

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By conducting two viral monitors per year, the world organization predicts which strain types will dominate for the current year so that producers modify the vaccine accordingly, to ensure maximum effectiveness.” From this moment, you have the product to be ready in six months to be shipped during August and time available in pharmacies when the campaign begins, “the director of Sanofi Pasteur industrial operation sites in France.

What contains the flu shot?

Once the recommendations are provided, the rest of the process “consists in multiplying the viral strains, which will be put in the vaccines, by the millions thanks to a technology on eggs“, explains the director of industrial operations. Introduce a germ into a living organism, to help it develop there.

Then after an incubation period, we perform purification, fragmentation, inactivation and filtration in order to obtain the four active ingredients of the vaccine which will trigger the body’s immune response against the virus”. After a period of storage and numerous quality controls carried out at each stage, the formulation is ready to be made in June.

In some vaccines, adjuvants can be added in addition to vaccine antigens to give it better efficacy.

A significant number of deaths avoided each year thanks to flu shot

From June, the process of filling the bottles in the chain is launched. “Between each step, quality control is carried out reviewing all the standards. At the slightest error, we stop and put aside the one that is wrong,” explains the director. Hundreds of boxes of syringes parade are shelled, filled, then packaged from room to room and from machine to machine.

Once the process is completed, the packages are prepared and shipped to pharmacies around the world by boat from France, plane or truck to respect the cold chain. The quantity to be manufactured each year is estimated on the basis of pre-orders from pharmacies since the previous December.

In the world, influenza affects a significant number of people every year according to WHO. Estimated deaths from seasonal influenza are between 290,000 to 650,000 per year. Up to 20% of deaths per year would be avoided each year thanks to the vaccination campaign.

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