The NHS is reportedly scrambling to get flu vaccines that protect against the life-threatening 'Aussie' strain amid an anticipated outbreak this winter.
Every February, the World Health Organization (WHO) assesses which three or four flu strains it expects to be circulating the following winter in the northern hemisphere.
Based on these recommendations, vaccine manufacturers start producing jabs in March.
However, the emergence of the H3N2 strain, which is behind one of the worst flu seasons ever in Australia, delayed the WHO's decision-making process by a month.
This means some vaccines may not be delivered to GP practices until November, rather than the standard September.
Flu season started unseasonably early in Australia, which is in its winter. The virus has already caused three times as many deaths as last year.
The NHS is reportedly scrambling to get flu vaccines that protect against the 'Aussie' strain amid an expected outbreak this winter. The H3N2 strain is behind one of the worst flu seasons ever in Australia, with a national death toll reaching 231 earlier this month (stock)
A letter, seen by The Telegraph, was sent by Public Health England and NHS England to all GP and community pharmacists in the country.
It warns the WHO's delayed decision-making is 'in response to a recent increase in the proportion of viruses detected which would not be effectively dealt with by its existing vaccine strains'.
It adds: 'We understand from manufacturers the delayed WHO recommendation on vaccine strain has had an impact on their vaccine supply.'
This comes after Australia's national death toll reached 231 earlier this month.
It has also had around 121,000 laboratory-confirmed cases - eight times more than normal.
There were more than 40,000 confirmed cases in June alone. This is the highest number ever recorded for the month and significantly more than the 2,000 recorded incidents last year.
And Australia is not even halfway into its flu season, which typically runs between May and September.
Experts have warned there is likely to be a second peak in cases later in the season.
Australia's flu vaccine is thought to be relatively ineffective against H3N2 because the jab was designed last September, with the strain then going on to mutate.
Professor Kanta Subbarao, spokesperson for the WHO's Influenza Centre, previously said: 'The H3N2 virus is the one we worry about because it affects the very young and the elderly.'
Elderly people are said to be less vulnerable to strains like H1N1 because they have encountered similar viruses before.
On the back of this, all UK GPs are being urged to contact flu-vaccine manufacturers to check when the jabs will be delivered.
They can then schedule immunisation appointments around this delivery date.
The delays specifically affect the quadrivalent jab, which protects against four strains of flu and is for adults aged 18-to-65 who are at an increased risk of flu but cannot have a 'live' vaccine.
This includes pregnant women and those with conditions like asthma or diabetes.
The pharma giant Sanofi Pasteur has suggested it plans to phase some of its quadrivalent vaccine deliveries, with some arriving in November.
Sanofi is one of four jab manufacturers that will be issuing vaccines this year.
'I'm so sorry I couldn't protect you': Shattered family's gut wrenching tributes to 'perfectly healthy' 13-year-old girl who died of the flu just hours after she started to get a runny nose
Shattered family members of a 'perfectly healthy' 13-year-old who died of the flu have issued heartbreaking tributes to the 'kind, smart and beautiful girl'.
Crystal-Lee Wightley came down with a fever, body aches and coughing on July 2, with her condition worsening over the next 48 hours.
Her mother, Dymanty Fulham, quickly scheduled a doctor's appointment early on July 5, but at 6.15am she found her daughter unconscious.
Paramedics soon arrived but Crystal-Lee was pronounced dead at their family home in Baxter, Victoria.
Crystal-Lee Wightley came down with a fever, body aches and coughing on July 2 and was sent to bed to recover. Three days later her condition had not improved. She soon feel into unconsciousness and sadly died in the family home
'Crystal was kind, smart, beautiful and had come backs that would make a room stop and then laugh,' her sister wrote.
She spoke candidly about Crystal's final days.
'On Monday I was sitting with her for the afternoon talking about baby names of her baby cousin she was getting ready to meet,' the devastated sister said.
'She was honest. She was caring and her heart was in the right place when to came to caring for the little people in her life.'
She said the entire family had been sick including her younger brothers and mother with Crystal the last one to catch the deadly virus.
'There was hope that she like everyone else was getting over the disgusting virus,' she said.
Several family members paid tribute with Joshua Gartland, her uncle, remembering his niece that had 'gone extremely too soon'
Family member Channi Gartland (left) wrote that 'Crystal was a kind, smart, beautiful' person who could always make people laugh
'We as a family will hold each other hands, cry, mourn, grieve and be together.'
She ended the tribute with a final and tragic message to her 13-year-old sibling that had passed too soon.
'Baby girl.. I love you. I miss you and I'm so sorry I couldn't protect you,' she said.
Several others paid tribute with Joshua Gartland, her uncle, remembering his niece that had 'gone extremely too soon'.
'It's with huge sadness and disbelief that my princess niece Crystal has passed away this morning,' Mr Gartland said.
Her mother, Dymanty Fulham (pictured), was one of many in the family who came down with the flu but, unlike the rest of the family, Crystal never recovered
'I miss you so much already moo. Your such a beautiful girl inside and out I love you so much and always will,' he said.
Crystal-Lee's aunt, Yvette Southgate, said the family was in denial over her sudden death. Just three days earlier, the teen was running around playing netball and football.
'We are all shattered, everyone is mourning. None of us thought we needed to go to the hospital, she was perfectly healthy and was giggling and laughing with her cousins days before,' she said to the Herald Sun.
'I miss you so much already moo. Your such a beautiful girl inside and out I love you so much and always will,' her uncle Joshua Gartland said
Crystal-Lee's grandmother Karyn James Wightley took to Facebook to share her grief.
'Big Poppy and Big Nanny will be waiting to put their arms around you and keep you safe until we meet again. Missed and loved always I just cant stop crying beautiful girl,' Mrs Wightley wrote.
Another family member, Pam John Gartland, posted simply: 'This life sucks, r.i.p. Missy Moo'.
Her death comes as the South Australian government announced a campaign to educated people on the dangers of the flu and how people can protect themselves
Crystal-Lee's death comes just days after flu claimed the life of a two-year-old boy in Perth.
Elijah Hunyh had only just turned two when he caught a strain of influenza. His devastated family said the virus 'spread like wildfire' overnight and they had no warning signs.
He was admitted to his local Karratha Health Campus for treatment.
Elijah Hunyh had only just turned two when he caught a strain of influenza. His devastated family said the virus 'spread like wildfire' overnight and they had no warning signs. Elijah is pictured with his father Dave
Though the Royal Flying Doctor Service transported him to Perth Children's Hospital as his condition worsened and his organs began to shut down.
In a matter of days, Elijah had passed away.
'You will always have my heart as with your mummies and your baby sisters . My first boy I’m so proud of you! Mummy and daddy love you unconditionally!,' his father Dave wrote online.
One-year-old Freddie Fields was recently diagnosed with mutated H3N2 after his parents rushed him to hospital when he was having trouble breathing. He is on the mend
'You were and still are the love of our lives, we couldn’t thank you enough for making us the happiest parents in the world.'
Children aren't the only ones that have struggled with the virus, with a 43-year-old father dying from its effects last month.
James Day, a hospital security guard in Victoria, battled influenza A for a week before he suffered 'catastrophic complications'.
James Day (pictured with his son Jackson), from Traralgon in Victoria, battled influenza A for a week before he suffered 'catastrophic complications'
The father was placed on life support but showed no signs of improvement and his former wife Jennifer made the tragic decision to let him go, leaving his young son Jackson without a father.
On June 16, a week before his life support was turned off, she wrote on Facebook: 'James has been battling Influenza the last eight days.
'Unfortunately it has hit him and his body quite hard and last night he was admitted to the Alfred ICU. He is very sick,' she said.
'Please send your thoughts this way, he very much needs it right now.'
It comes as the South Australian government announced a campaign to educated people on the dangers of the flu and how people can protect themselves.
Before her husband's death, Mrs Day made a heartbreaking post on Facebook thanking friends for their support. The couple are pictured on their wedding day