According to Dr Jenny Harries, chief executive of the UK Health Security Agency, people who have both flu and Covid are twice as likely die than those who have only coronavirus.
Former deputy chief medical officer for England warned of an uncertain winter in the UK with flu and Covid-19 first-ever circulating. He urged people to get flu jabs and coronavirus vaccines, if they are available.
When asked by Skys Trevor Phillips on Sunday how concerned she should feel about flu this winter, she said: "We should be concerned about flu every winter. It can be fatal, I believe.
The important thing is that flu will likely be seen in this winter, possibly co-circulating with Covid. There are still risks of getting both. Early evidence suggests that two or more of your covids together could make you twice as likely to be killed than one.
She said that although it is not an omen, but a feature, we know that influenza cases are lower this year, so the immune system and strain types are more uncertain.
Harries warned that the UK could be hit by multi-strain flu. The UK's immunity will be lower this year due to last year's Covid restrictions.
According to her, flu kills approximately 11,000 people each year. This is due to the fact that we have not had flu for as long as we would like. Although it is possible to get multi-strain flu, we are more likely to get one strain.
Harries stated that there are four types of flu virus in this year's flu vaccine. He took advice from the World Health Organization, the Joint Committee on Vaccination and Immunisation and looked at countries in the southern hemisphere where flu season and winter arrive earlier.
We have a lot of options to choose from, but there could be many this year and people will be less immune. Harries said that the trick is to get vaccinated for both flu and Covid. However, it's important to keep up with good hygiene habits we have been practicing all through Covid.
Harries stated that children wearing masks to school is not a top-of-her list of Covid safe measures.
It is important that we make sure that children are not in school if they have an infectious disease. She said that we have a good testing program and expected to see an increase in cases at the beginning of each term.
Harries stated that the global dominance of the Delta virus variant has led to other coronavirus variants becoming extinct. However, he warned that we must remain vigilant.
The NHS is aiming to immunise a record number of people this winter. This is the largest ever programme of flu jabs. For approximately 30 million people over 50, social workers, pregnant women, and those at high risk of becoming ill, flu shots are free.