The man behind the most signed online petition in parliamentary history is "speechless and overwhelmed" by the response to the campaign to give all children the meningitis B vaccine.
More than 640,000 people have now signed the petition set up by Lee Booth, beating the one organised to ban US presidential hopeful Donald Trump from the UK.
Father-of-two Mr Booth, 44, said it would now be difficult for the Government to ignore the groundswell of support to vaccinate all children up to at least the age of 11.
Mr Booth launched the petition last September after one of his two young daughters was deemed too old to have the vaccine on the NHS.
The campaign attracted around 900 signatures until two-year-old Faye Burdett, from Maidstone, Kent, caught the infection and died on Valentine's Day after an 11-day battle.
A flood of support followed after a harrowing picture of Faye covered in a rash and lying in a hospital bed just before she died was shared by her family.
Now the petition has gained more than 100,000 signatures, a debate is guaranteed to be held in Parliament.
British Gas worker Mr Booth, who lives in Newcastle-upon-Tyne, said: "I'm speechless and overwhelmed by the response. It has been phenomenal.
"I have spent quite a lot of time responding to tweets and Facebook messages. The number of signatures has just sky-rocketed. The Government cannot now ignore the biggest petition ever."
Faye's parents, Jenny and Neil, have said the response to the petition since their toddler contracted meningitis B and died has been "overwhelming".
The plight of meningitis sufferers was raised further when ex-England rugby captain Matt Dawson told how his two-year-old son Sam battled meningitis C.
Although his son is now well and back home with his family, Dawson said he felt "absolutely helpless" as Sam lay hooked up to machines in hospital.
A vaccine to protect against meningitis B is available on the NHS for babies aged two months, followed by a second dose at four months and a booster at 12 months.
But parents who wish to have older children vaccinated must pay privately, although a worldwide shortage of the vaccine Bexsero means stocks are very low.
Manufacturer GlaxoSmithKline (GSK) hopes to have increased stocks in the UK by the summer. The NHS programme is unaffected.