More than 6,000 people are bidding to be stem cell donors to help a boy facing a race against time to beat leukaemia.
Oscar Saxelby-Lee, five, needs a transplant within three months of his chemotherapy or his chances of survival will “severely diminish”.
More than 1,000 were swabbed at an event in Worcester on Saturday on top of the 5,000 tested last weekend.
“It’s fantastic to see how many people care,” said organiser Louise White.
The latest event to join the NHS blood stem cell register was held at the Guildhall in Worcester, following on from a sign-up session at Pitmaston Primary School where thousands queued in the rain.
Among those being swabbed was Worcester MP Robin Walker.
At the scene – Phil Mackie, BBC News correspondent
It has been a Herculean effort by the city – six-thousand people is about 10% of the eligible population in Worcester, because you could only participate if you are older than 16 or younger than 55.
A further event at Worcester University later this week will increase numbers further.
It has not stopped under-16s participating. There was a small army of Year 10 and 11 pupils from the Blessed Edward Oldcorne school, aged 14 and 15, acting as marshals at today’s event or walking the city streets to publicise what was happening and rounding up more volunteers.
The campaign to help Oscar has captured the imagination of young people in the city who are really doing their bit.
Swabs will be tested by DKMS, the charity that fights blood cancer, in the hope one of the donors will be a match for the boy.
Oscar became unwell over Christmas and his mother Olivia Saxelby, 23, and father Jamie Lee, 26, thought he was anaemic.
Following a blood test, he was diagnosed with acute lymphoblastic leukaemia .
A stem cell transplant replaces damaged blood blood cells with healthy ones.
Often, a close family member with the same type of tissue can donate the cells but neither of Oscar’s parents are a close enough match.
Many of those joining the effort are young people, as experts say it is most likely a match will be found amongst those aged between 17 and 30.
Oscar is being treated at Birmingham Children’s Hospital, and organisers said more events would be taking place to attract more possible donors.
Family friend Jo Martyr, who was at Saturday’s event, said: “Oscar is still OK, he’s braving it, he’s getting through this treatment but he needs that match – he needs that chance of life.
“The people from DKMS said they’d never seen anything like what has happened these last two weekends in Worcester.”
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