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Babies increased risk of flu if they have older siblings

Babies are at twice the risk of suffering severe flu if they have an older brother or sister, a study found.

Children are ‘effective spreaders’ and can easily pass viruses onto their vulnerable younger siblings, researchers said.

Flu can be life-threatening in young children because it can cause lung infections, breathing difficulties and high fever, which can lead to fits.

Between 3 per cent and 11 per cent of babies and toddlers in developed countries acquire flu-associated illnesses each year, placing a heavy burden on health services.

Almost half of all cases of severe flu in babies under six months old are caught from older siblings, according to a study by University College London’s Great Ormond Institute of Child Health.

Children are ‘effective spreaders’ and can easily pass viruses onto their vulnerable younger siblings, University College London researchers said

Experts warned parents the findings showed the importance of getting older children vaccinated to protect babies in the family – who usually are not given a flu vaccine before the age of two.

Lead researcher Dr Pia Hardelid said: ‘Flu can be a serious infection in very young children but at the moment there is no vaccine approved for babies under six months. This means we need to look at other ways to minimise the risk of infection.’

How was the study carried out? 

Researchers studied 424,048 children – almost all those born in Scotland between October 2007 and April 2015.

They used anonymised hospital data to find out how many children had been admitted to hospital with flu and compared this with other basic information, such as when they were born, whether they were premature or had other health conditions, and whether they had older siblings.

What did the results show? 

The results showed that 1,109 children were admitted to hospital with flu once and six were admitted twice.

Children under six months old with an older sibling were more than twice as likely to be admitted to hospital with flu than those who were the first child in the family.


The dreaded Aussie flu outbreak that the NHS is preparing for will be the worst in 50 years, experts warned earlier this week.

Some A&E units in Australia had ‘standing room only’ after being swamped by more than 100,000 cases of the H3N2 strain.

Professor Robert Dingwall, a public health expert at Nottingham Trent University, said it is ‘inevitable’ it will reach Britain.

He said it could claim as many lives as the Hong Kong flu outbreak in 1968, which killed at least one million people.

Professor Dingwall told The Daily Express: ‘Based on the Australian experience public health officials need to meet and urgently review emergency planning procedures.

‘Public Health England should be working with local authorities and local health services to ensure more hospital beds are freed up. We need to be prepared, alert and flexible.

‘There is no point in trying to close the borders. It’s almost inevitable this will come to us. 

For those with two or more older siblings, the risk tripled.

There was around one extra hospital admission for every thousand children who had one older sibling. In those with two older siblings, there were two extra admissions per 1,000 children.

Babies born between July and December – who would be young and vulnerable at the start of the flu season – were also at higher risk.

Nasal spray vaccines 

Since 2013, nasal spray flu vaccines have been given to children aged between two and nine on the NHS. Some areas are rolling out the vaccine to all primary school-age children.

It is also offered to those aged up to 17 and from six months to two years who are considered high risk because of existing chronic health problems.

The researchers said vaccinating older children could have a protective effect on babies and toddlers. Pregnant women could also have the vaccine to help build up their baby’s immunity.

The importance of the flu jab 

Dr Hardelid added: ‘Our study suggests that older siblings pose a risk of serious infection for their baby sisters and brothers.

‘The nasal spray vaccine, which is now being offered in GP surgeries and primary schools in the UK, provides a good opportunity to protect the children who receive it, as well as their younger siblings.

‘There is not much parents can do about the time of year their baby is born, but women can also help reduce the risk of serious flu for their newborns by taking up the invitation to have a vaccine when they are still pregnant.

‘There is some evidence that maternal vaccination during pregnancy can protect young babies from flu infection.’

Rates of hospital admission were also higher for children aged six to 23 months with older siblings, but the association for this age group was much weaker.

Further research will test whether the introduction of the vaccine for children aged two and older can help reduce cases of flu among under-twos.

The study was published in the European Respiratory Journal.