Fewer people came forward for their flu vaccine last year and if the same happens again the UK could be in for a worse winter, health officials are warning.

There were at least 18,000 flu-related deaths over the last couple of years, despite being relatively mild flu seasons, according to the UK Health Security Agency (UKHSA).

Free flu shots are offered each year by the NHS to people most at risk from getting very sick with flu, also known as influenza.

While uptake among older people in England remained high last year, only one in every three pregnant women got vaccinated. Among people with long-term health conditions, uptake was about four in 10, compared to five in 10 the year before.

Vaccinations for two and three-year-olds were also down slightly, with just over four in every 10 getting protected.

It follows concerns from NHS England over a possible “tripledemic” of flu, Covid and respiratory syncytial virus (RSV).

People can catch these common viruses all year round, but flu is especially common in winter.

Most make a full recovery from influenza, but it can be serious and even deadly.

Some years are worse than others for flu infections and fatalities. In the 2017 to 2018 season, there were 22,500 excess deaths associated with flu.

It is not clear how bad this year might be.

Northern hemisphere nations, like the UK, look to southern hemisphere ones, like Australia, to predict what could be coming.

Australia’s winter flu season looks to be ending and data reveals that it was similar to recent ones.

Southern Africa and some countries in South America – Chile, Ecuador, and Uruguay – had high levels of flu though.

The vaccine is updated regularly to make sure it is the best possible match, because of the constant evolving nature of influenza viruses.

People are offered a free NHS flu vaccine if they are:

• aged 65 or older
• have certain long-term health conditions
• are pregnant
• live in a care home
• are the main carer for an older or disabled person, or receive a carer’s allowance
• live with someone who has a weakened immune system

Some people will have already received an invitation, and most eligible adults will be able to get the flu vaccine from 3 October

Children are offered an up-the-nose spray flu vaccine.

People can have the flu vaccine at the same time as other jabs such as those for Covid and shingles.

It is not usually given at the same time as the RSV vaccine, but you can have them together if a doctor or nurse thinks it is needed.

Dr Gayatri Amirthalingam, UKHSA deputy director of immunisation, said: “As winter approaches we see many dangerous viruses circulating in our communities including flu, which can tragically kill thousands of people every year. Getting vaccinated ahead of winter is by far your best defence.

“If you’re pregnant or have certain long-term health conditions, you are at greater risk of getting seriously ill. Older people and young infants with flu are also much more likely to get hospitalised.

“So if you or your child are offered the flu, Covid or RSV vaccines, don’t delay in getting them. Please speak to your nurse or doctor if you have any concerns.”

Those eligible for an autumn Covid booster include adults aged 65 or over, care home residents, staff, front-line health and social care workers, and people in clinical risk groups, including pregnant women.