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Influenza: when to get the flu shot?


What time of year is it recommended to get the flu shot? Can we still get vaccinated late in the season? Why repeat the vaccine every year? Are we all affected by influenza vaccination? Explanations and recommendations.

When to get the seasonal flu shot

Low temperatures, low humidity… These are the weather conditions conducive to the circulation of viruses! In the northern hemisphere, the seasonal flu epidemic thus begins in the fall and generally continues until the end of winter.

To counter it, the influenza vaccine campaign starts in October and lasts four months. This vaccination schedule aims to anticipate the viral peak generally reached in January.

The health authorities, therefore, recommend that the population be vaccinated each year, and at the earliest preferably from mid-October or during the month of November.

For latecomers, it is still possible to get vaccinated against this virus late in the season. However, be aware that once the vaccine is administered, it will take fifteen days for the antibodies to take effect.

Why do you need to be vaccinated every year?

Six to nine months: this is the length of time that the antibodies will persist in your body. After this period, you will no longer be protected against the flu. This is the first reason why it is essential to renew this vaccine every year.

The second? New viral strains come into circulation every year. Seasonal influenza epidemics are caused by constantly changing type A and B viruses.

The influenza vaccine thus contains three or even four viral strains. These type A and B strains are selected each year by a group of scientific experts, depending on the viruses circulating in the year in question. The composition of the influenza vaccine thus varies from year to year. 

What is the composition of the 2019-2020 influenza vaccine?

In accordance with the recommendations of the World Health Organization WHO, the 2019/2020 vaccine contains the following viruses:

  • A virus type A / Brisbane / 02/2018 (H1N1) pdm09 (currently predominant globally); 
  • A virus type A / Kansas / 14/2017 (H3N2);
  • A virus type B / Colorado / 06/2017 (line B / Victoria / 2/87);
  • A virus type B / Phuket / 3073/2013 (lineage B / Yamagata / 16/88).

Only two tetravalent influenza vaccines (composed of these four strains) are available for winter 2019-2020 are Influvac Tetra and Vaxigriptetra. The Influvac Tetra vaccine is indicated from the age of 3, while the VaxigripTetra vaccine can be administered from the age of 6 months and in pregnant women at any stage of pregnancy. In addition, the FluarixTetra vaccine, which was available during the previous season, will not be available this year.

What does the 2020-2021 influenza vaccine contain?

The composition of the influenza vaccine for winter 2020-2021 has been changed from that of the previous year. It includes viruses belonging to the following strains:

  • virus type A / Guangdong-Maonan/ SWL1536 / 2019 / H1N1pdm09,
  • virus type A / Hongkong/ 2671/2019 / (H3N2),
  • virus type B / Washington/ 02/2019,
  • virus type B / Phuket /3073/2013.

For the campaign 2020-2021 influenza vaccination, two vaccines quadrivalent (which protect against four virus strains) are available and supported: InfluvacTetra and VaxigripTetra.

How does the flu shot work?

The body, in contact with fractions of the virus rendered harmless, will develop antibodies, specific immune defenses which will protect it against the virus. Count “about 15 days after vaccination to be protected against the flu”, the time for the immune system to react.

Flu vaccine: who is affected?

Influenza is a serious global health threat that affects all countries: each year, an estimated 1 billion cases, 3 to 5 million severe cases, and 290,000 to 650,000 respiratory deaths from influenza are estimated globally. A mostly mild infection can be cured in a few days. The prescription is succinct: rest, rehydration and taking antipyretics in case of fever.

And yet, the flu is responsible for a large number of medical complications each year that can lead to death. Among the subjects most exposed to medical complications:

  • People aged 65 and over;
  • Pregnant women ;
  • Children under 5;
  • Individuals suffering from obesity;
  • Individuals with certain chronic diseases. 

The health authorities thus count a large number of people who are medically vulnerable due to a weakened immune system. In these people, the use of the influenza vaccine is strongly recommended.

It is now possible to be vaccinated directly by your pharmacist as is the case in France and other European countries. A device that remains reserved for people “at-risk”, with the exception of pregnant women.

The health authorities also insist on the high risk of transmission of the virus by air, in the event of coughing or sneezing in particular. Thus, the flu vaccine remains recommended for people in regular contact with individuals at risk of complications. The same is true for health professionals.  



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