The very same drug that helps men with erectile dysfunction has given the one-year-old a lifeline.
Alfie was born last July with a narrowing of the blood vessels around his lungs and was given just weeks to live, reported the Daily Telegraph.
He was born with two of his main arteries reversed and surgeons switched them when he was 16 days old.
During a second operation at three months, he had a heart attack and was rushed to intensive care.
Parents Tracey, 26, and Rob, 28, were told he was unlikely to survive and were put in touch with a children's hospice, reported the Sun.
Then a team of experts from Britain's Great Ormond Street Hospital heard of his story. They suggested a radical solution - give him Viagra.
Mrs Oliver told the Telegraph: 'When they sat us down and said he needed Viagra, we thought 'oh my goodness'.
'It's such a strange thing for a baby to be on, but it's literally saved his life.'
The liquid Viagra he was given opened up the vessels and improved Alfie's circulation.
He is now doing well and learning to walk, although doctors have warned he may one day need a heart and lung transplant.
Thankfully, because of his young age, Alfie does not experience the renowned side effects of the drug, reported The Press in York.
'His first year has been very traumatic,' said MrsOliver. 'But we just treat him as our brave little fighter and we are incredibly happy that he has got to his first birthday.
'We call it (Viagra) Alfie's life saver.
'It makes people giggle when we tell them - but if it keeps our son alive then who cares.'
