The Call The Midwife star has the gene that causes the lung condition and has a niece and great nephew with CF.
Kaftrio has been called a near-cure for many sufferers and it has transformed lives. But National Institute for Health and Care Excellence advisers have said it is not cost-effective to prescribe it on the NHS.
The Daily Express, which is spearheading a crusade to have the drug approved, led the fight for it to be made available four years ago.
Some 8,000 patients use Kaftrio and it is thought they will be able to stay on it and related drugs – but 2,000 babies too young for it yet may miss out.
The actress’s niece Rachel McGrath, 45, was given a new lease of life after starting the drug in 2019 but great nephew Albie has a form of CF that makes it unsuitable.
Jenny, 71, said she had been inundated with messages from parents and said: “The series of drugs that include Kaftrio are revolutionary. Restricting their prescription on the NHS would be a death sentence for a whole generation.”
“There will be families…whose toddlers qualify for Kaftrio but who may go on to have other children with the condition that miss out.”
“How can that be right? These drugs are expensive but surely not as costly to the NHS as CF patients whose health will be so much worse without them.” Rachel added: “I hope it won’t get to the stage that Nice stops funding Kaftrio.”
Made by US firm Vertex, it costs about £200,000 per patient per year.