Isaac Sheard, 13, who also has a number of other health conditions, got his jab a week ago after his mother, Ann-Marie Sheard, managed to negotiate between consultants and GPs to get permission.
Ms Sheard, from Ackworth, said she does not blame clinicians for being wary about allowing vaccinations as the jabs have not yet been approved for use in under 16s.
The mum-of-six said Government action is needed to clarify the situation so many more extremely clinically vulnerable youngsters can be protected.
"There's no safety net for clinicians putting their necks on the line and saying 'yes, ok, get him vaccinated'," Ms Sheard told the PA news agency.
"If something were to go wrong, it's on them, isn't it?
"The guidelines the Government have given aren't clear enough."
Ms Sheard described the strict shielding regime her family has lived under for the past year to protect Isaac, who has been told is at high risk of being seriously ill if he catches Covid-19.
Even when his four brothers had to return to school in the autumn, they each went through a thorough strict decontamination routine every time they returned to the house.
Isaac is due to return to his school in mid-April and this prospect fuelled Ms Sheard's determination to get him the jab.
She said clinicians' "hands are tied" and parents have to rely on individual GPs being prepared to seek permission from specialist doctors and that approval being forthcoming.
Ms Sheard said: "We hit this brick wall of 'it's not licensed; it's not approved for this age group'."
But she finally persuaded one of her son's consultants to give his GP the approval needed.
"Although myself and my husband have been vaccinated the person that we really needed vaccinating was Isaac because he's the one that's at most risk of being the most ill," she said.
"When the phone call came through I was like 'am I hearing this correctly?'.
"It was brilliant.
"It's a massive weight off our minds. We're not out of the woods yet. We're fully aware that the vaccine doesn't stop him from getting Covid.
"What it does is reduce his chance of being severely ill and that's all we can hope for."
Ms Sheard said: "It's a massive step forward but the frustrating thing is that so many other families are hitting that brick wall.
"Until we get someone to say 'these are the guidelines - if these children have this condition then we advise them to have the vaccine' then a least the clinicians and the GPs have got something solid to go from. But, at the moment, they haven't."
She said the "euphoria" she should be feeling about Isaac getting vaccinated has been muted because "our community aren't fully protected".
Isaac said he is looking forward to going back to school as he had really missed his friends.
A Department of Health and Social Care spokesperson said: "Almost all children with Covid-19 have no symptoms or only mild disease.
"For a very small number of children at a higher risk of catching the virus and serious illness, the Joint Committee for Vaccination and Immunisation (JCVI) have advised that vaccination can be appropriate.
"JCVI advise that this is a decision for doctors and clinicians to make on a case-by-case basis and should be a carefully discussed between a child's parents or carers and their GP."
The JCVI advice is that vaccination is not usually recommended for the vast majority of children under 12 and, for children aged 12 to 15 years, vaccination may be appropriate for those with severe neuro-disabilities who tend to get recurrent respiratory tract infections and who frequently spend time in specialist residential care settings.
Deputy chief medical officer Jonathan Van Tam said in January: "The JCVI advice is that for children who are extremely at risk there can be a discussion between their physician and the parents about the benefits of vaccination in children under the age of 16 years of age.
"That would nevertheless be use of the vaccines as they currently stand in an off-label and off-licence way, and therefore it needs to be a carefully discussed, individual decision with the physician and the parents."