One study found they are 10 times more likely to die from the virus, while another pegged it at three times more likely.

But there's no doubt that people with DS are at higher risk of death from the disease, and they are just one group in the community who have more skin in the game than the average person.

Which makes parenting one of these vulnerable children a tough gig, as the Delta variant continues to sweep through NSW and the Government talks of opening up schools next term.

"The stakes are really high for us," said Sarah, a primary school teacher, whose son Harry, almost five, has DS.

Sarah, husband Carl and their three children live in Robertson, on the NSW southern highlands, where she feels safe while lockdown continues.

But the thought of going back to some kind of "normal" with a percentage of people still unvaccinated has her concerned.

She said that the issue of vaccination had become a particularly fraught and emotive one for her, as she watches the debate among some sectors of the community continue with seemingly little thought for the safety of those with the most to lose.

"Down Syndrome comes with a lot of health issues anyway, and a lot of parents are scared of sending kids back into school and group environments along with unvaccinated kids and adults," Sarah said.

"Parents of kids with DS or disability in general already have such a heavy weight to carry, that most people don't know about - the burden is so great for those people and this is bigger burden that we have to carry."

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Researchers suspect that immune abnormalities, plus extra copies of key genes in people with DS, make them more vulnerable to severe COVID-19.

Sarah is aware that there are people in her immediate community who are choosing not to get vaccinated.

"It puts us in a tricky spot - do we just not ever go anywhere again?" Sarah said.

"I don't necessarily agree with mandating vaccination, but I want people to look at things from our perspective.

"I've heard people say it's so unfair that teachers have to be vaccinated - but it's a bit unfair to place this burden on us.

"I understand there are some people with valid reasons to not get vaccinated, but when it's just a personal choice, I struggle with that - there's an element of selfishness to it.

"I have another friend with a child with cerebral palsy who's in an out of hospital all the time - what would it do to him? It's just a hard pill to swallow, and it feels unfair."

She urged those who are vaccine hesitant to "think this through".

"I don't want to guilt people into that decision - but I want them to see it's the responsible, right thing to do," Sarah said. "I just want them to make that decision for themselves, to care for others, because otherwise it can put families like ours in an awkward position.

"There are parents of kids with DS who have gone through multiple heart surgeries and have lung problems, and they're really scared."