Episode #90 - Influenza

13 January 2023 | Science conversation

 Vismita Gupta-Smith

We are talking about influenza today. How does the vaccine combat the influenza virus? How is the composition of the vaccine decided? And how does WHO track the influenza virus across the world?

Hello and welcome to Science in 5. I am Vismita Gupta-Smith. We are talking to Dr Sylvie Briand today. Welcome Sylvie. Before we talk about influenza, speak to us, please Sylvie, about this spike in respiratory disease that we are seeing and the reasons for it.

Dr Sylvie Briand

Indeed we are seeing a spike in respiratory viruses, all kind of viruses, COVID 19, Influenza, RSV. This is not a surprise. We always see an increase in respiratory diseases in winter time for the northern hemisphere. Why?

Firstly because most of the 175 types of circulating respiratory viruses prefer cold and humid weather. Most of them produce mild disease, but some of them like COVID-19, influenza or RSV can produce severe disease leading to hospitalization and even death.

Secondly, when the weather is cold or humid people tend to gather indoor, in less ventilated spaces and thus are more exposed to infection.

However, this year is a bit special. We are seeing more respiratory diseases than usual. We think that this increase is due to at least 2 factors:

In the past three years people were applying personal protective measures like mask, washing hands, less gatherings. But this year, in many countries, most of these preventive measures are not applied anymore.

In addition, people have probably lost some of their immunity against respiratory viruses in general, given the low circulation of respiratory viruses in the past years thanks to the protective measures. 

Vismita Gupta-Smith

Sylvie, talk to us about the influenza virus and how the vaccine combats it?

Dr Sylvie Briand

There are many influenza viruses circulating. We know at least three big families: AH1N1, AH3N2 and B viruses. What is important to know is that these viruses evolve constantly. As they multiply in human cells, viruses are changing. This is like having a “parent virus” making many children and then having many grandchildren and many great grandchildren.

The influenza vaccine, it's like a picture of the virus: a picture of the enemy that is shown to our internal defenses, the antibodies. When the antibodies have seen the picture of the virus. They can recognize it. 

So when the virus enters the body, the antibody can push it out. This is how the influenza vaccine works. 

However, because of the constant evolution of the virus, we need to update the influenza vaccine composition regularly, so that the picture of the enemy that is shown to the antibodies is not the picture of the parent virus that was circulating last year but the picture of the great grandchild viruses that are circulating this year.

Vismita Gupta-Smith

Sylvie, speak to us about how WHO tracks the influenza virus across the world?   And how is the composition of the vaccine decided?

Dr Sylvie Briand

The WHO has a network of laboratories around the world called GISRS, the Global Influenza Surveillance and Response System.This network is composed of more than 150 laboratories in 137 countries. Those laboratories are collecting and monitoring influenza viruses throughout the year. The collected viruses at the national level are then sent regularly to WHO collaborating centers for global assessment.

Experts meet regularly to monitor the circulating viruses, assess which ones are predominant and then define which ones should be considered for the vaccine, so that the picture of the enemy is the best possible picture to train our antibodies to fight the virus. This represents an enormous amount of work. But many countries in the world are participating in this effort because influenza is an important public health issue and is killing between 200 to 600 thousand people every year which represents nearly 8000 deaths per week on average. So the influenza vaccine is safe and very effective to protect against severe disease, hospitalizations and death.

It is strongly recommended for people at risk of severe disease such as elderly, people with underlying conditions and co-morbidities like immunosuppression, diabetes, chronic respiratory and cardiac diseases and so on.

Influenza vaccine is also recommended for pregnant women and young children. We also encourage health care workers to get vaccinated as they are more exposed to the virus in their professional practice, and they are less likely to infect their patients when vaccinated.

Vismita Gupta-Smith

Thank you, Sylvie. That was Science in 5 today. Until next time then, stay safe, stay health and stick with science.