Only 65 per cent of prisoners in WA are double or triple-dose vaccinated against COVID-19, according to figures released by the state government.
As of February 22, only one facility, Bandyup Women's Prison, had a booster vaccination rate higher than 70 per cent.
The next highest was Broome Regional Prison, at 31 per cent.
Not a single inmate at four adult prisons — Boronia, Greenough, Melaleuca and Pardelup — has had a booster, while the rate at several other prisons is less than one per cent.
Premier Mark McGowan last week urged prisoners to get vaccinated, after a guard tested positive at Acacia prison.
But Human Rights Watch researcher Sophie McNeill said prisoners were not being provided adequate access to jabs.
"Human Rights Watch wrote to the WA Department of Justice and Minister [Amber-Jade] Sanderson's office in early February to raise our concerns that prisoners at Hakea and Melaleuca prison have not [had] a vaccine clinic since late November."
A state government spokesperson said all prisoners in WA have had the opportunity to access vaccinations.
"Phase 3 of the vaccination program for all prisons and detention centres started on 15 February," the spokesperson said.
They said more than 1600 prisoners had received a dose since, and clinics were set to be implemented in prisons across the state in coming weeks.
"Following this phase, a rolling vaccination program will start to support all facilities."
Teen inmates' jab rate 'shockingly low'
Less than 30 per cent of prisoners in youth detention centres have received at least one dose.
By comparison, more than 98 per cent of people aged 12 to 15 in WA have had one or more doses.
Ms McNeill said the vaccination rates in prisons were "shockingly low".
"The failure by the department to have a continued, rolling vaccination program across all WA prisons could have real, devastating consequences," she said.
"Prisoners are at a heightened risk from COVID-19 due to a higher rate of underlying medical conditions than the general population and inadequate healthcare."
Slow action on prison booster rates
Shadow Corrective Services Minister Peter Collier said the state government had spruiked the importance of high triple-dose vaccination rates, but failed to act in a timely manner for the prison population.
"Around one in 10 prisoners are fully vaccinated at this stage," he said.
"The government has been telling us ad infinitum for months and months that it is imperative that we get fully vaccinated with a booster dose."
Mr Collier said there had been plenty of time to vaccinate the state's prison population.
"We're going to have a situation where we're going to have a massive infection rate of prisoners," he said.
"You've got a group of people here that are in a very confined space for obvious reasons which means, should there be an outbreak, particularly of the Omicron variant, they are extraordinarily vulnerable."
