The story of how two young lives were changed by blood donation brought several donors to tears on Wednesday.

Alexa MacDonald and her twin sister Julia, both 11 years old, were born 10 weeks premature. On Christmas Eve 2001, baby Alexa developed a deadly infection and needed a blood transfusion — a procedure that saved her life with just one unit of blood.

Now, Alexa and Julia are paying it forward. On Wednesday, they thanked people donating blood at Canadian Blood Services in Halifax. It was the first time they visited a blood donation clinic.

"We wanted to thank them because every donation pretty much saves a life," said Alexa. "Somebody donated during the busy holiday season and that saved my life."

Holiday campaign

The twins, from Enfield, were taking part in the kickoff of a campaign by Canadian Blood Services to help encourage blood donation over the holiday season.

Babies present unique circumstances, because they require blood donated within five days of a transfusion, their mom said.

"It was truly our miracle," said Heather MacDonald, who now works in the lab for Canadian Blood Services. "From day one, they went through all their struggles together and their victories and they're both very healthy now and inseparable."

The twins met with Arlene Seto, who has donated blood more than 10 times. Seto was brought to tears by their story.

"It's a very touching story," she said. "A good friend of mine actually, she gets blood products as a treatment for her illness, so that's part of the reason that motivates me to keep coming back.

"I'm very glad that they're doing well. I'll continue to give, knowing these stories and the impact it makes."