Health officials are urging people to get a flu vaccination before winter.
More than 40 million people will be offered the jab, amid fears the months ahead could see a surge in flu alongside a rise in Covid cases.
Who will get a free flu jab?
In England the flu vaccine is being offered free to:
- All children aged two and three
- All primary and secondary school pupils up to and including Year 11
- Those aged six months to under 50 years in clinical risk groups
- Pregnant women
- Those aged 50 years and over
- People in residential care
- Unpaid carers
- Close contacts of people with weakened immune systems
- Health and care staff
For most people the flu vaccine will be be offered via GPs, midwives and schools. Eligible patients can also book an appointment at a pharmacy.
What about free flu jabs in the rest of the UK?
Health officials in Scotland, Northern Ireland and Wales plan to cover similar groups - with some variation.
In Scotland, teachers, nursery teachers and support staff in close contact with pupils are being offered the jab.
In Northern Ireland secondary school children in their first year can have the vaccine. Older children are eligible if they are at risk.
Can you pay for a flu jab?
People not included in these groups can pay for a flu vaccine at pharmacies or some supermarkets, at a cost of about £15.
However, officials say vaccine supplies will be prioritised for people most at risk.
How bad is flu and how long does it last?
For many people it will typically last about two weeks, and get better on its own.
However, for some, flu can be very serious - particularly for older adults, very young children and people with underlying health conditions.
The added concern this year is that some of these people are also at greater risk of getting seriously ill from Covid.
Annual flu deaths vary each year, depending on the strain and other factors. Social distancing is likely to have helped to keep the number low last year.
There were more than 22,000 estimated deaths in the 2017-18 season, but just under 4,000 deaths in 2018-19.
Symptoms - is it flu or coronavirus?
It can be hard to tell if you have flu or coronavirus as they sometimes share similar symptoms, including:
Some people may also experience muscle aches, a headache, sore throat and diarrhoea and vomiting with flu.
But these symptoms can be seen with other common winter viruses too.
If any doubt, it's best to get a test.
Flu and coronavirus can also be spread before people have symptoms.
Could I get Covid and flu at the same time?
Yes, in which case you are more likely to be seriously ill.
Research shows those infected with both viruses are more than twice as likely to die as someone with Covid alone.
Can I get flu and coronavirus jabs at the same time?
About 30 million people in the UK are being offered a booster jab against Covid, including the over-50s and younger adults with health conditions.
They may be offered the flu and booster jab at the same time - but only if it's practical.
Deputy chief medical officer for England Professor Jonathan Van-Tam has said that it's safe to have both jabs simultaneously, and doesn't affect how well they work.
Are there side-effects to the flu jab?
Most side-effects are mild and only last a day or two, including a slightly raised temperature, muscle-ache and a sore arm where the needle went in.
Allergic reactions are rare but you should avoid the vaccine if you have previously had a serious allergic reaction to a flu vaccine.
People who have allergies to eggs should consult their pharmacist or GP to get a low-egg or egg-free vaccine.
It is best to avoid the vaccine if you are ill with a high temperature. You should re-book for when you are fully recovered.
Why is the flu jab different for adults aged 65 and over?
There are several types of flu vaccine.
Children will typically be offered the vaccine via a a nasal spray. Adults are offered injections.
For adults aged 65 and over the most common vaccine includes an extra ingredient that triggers a stronger response from the immune system.
If you are getting your vaccine on the NHS, experts say you will be offered the one that is most effective for you - depending partly on your age and taking into account vaccine stocks.