Prisoners and prison staff need to be prioritised for Covid-19 vaccines, researchers from University College London have said.

A new study published in the Lancet Journal of Respiratory Medicine said overcrowded facilities and inconsistent access to sanitation made prisons high-risk environments for infectious disease outbreaks.

Researchers said despite prisons implementing extensive social distancing and infection control measures in March 2020, there were 7.6 confirmed Covid-19 cases per 1,000 people in prisons in England and Wales during the first wave – compared with 4·9 in the general population.

The study also said there were 121 Covid-related deaths among people in prisons in England and Wales between March 2020 and February 2021, which is 3.3 times the rate of death among people of the same age and sex in the wider community.

However, the Ministry of Justice (MoJ) told the BBC the latest figure had been adjusted down to 118 per 1,000 – but was 93 per 1,000 for those who died directly from Covid rather than within 28 days of a positive test.

An MoJ spokesperson said in a statement to the broadcaster: “The suggested death rate is highly misleading and fails to take into account tens of thousands of additional offenders who move in and out of prisons every year.

“We have protected the lives of thousands of staff and prisoners – deaths are significantly lower than predicted and cases have fallen for seven consecutive weeks, as our strict measures limit the spread of the virus.”

In their report, researchers also stressed the impact the pandemic has had on prison staff, referencing a tweet from the Prison Officers’ Association which said there has been 20 deaths among staff up to mid-January 2021, as well as 4800 staff absent during that period.

Researchers say the high-risk nature of prisons should make them “one of the most pressing … priorities in the Covid-19 vaccination programme.”

The report states: “Currently, people in prisons are being offered Covid-19 vaccines in step with the general UK prioritisation criteria – ie, based on age and presence of long-term conditions.

“It can be difficult to identify eligible people in prisons, due to poor clinical coding and limited interaction with health services, both during and before prison. Many people in prisons are therefore considered low priority by default.

“Without a whole-prison approach, prisons will not achieve a good level of protection, or be able to safely restart family visits and vital educational and rehabilitation activities, until late in the roll out.”

The Joint Committee on Vaccination and Immunisation (JCVI) told the BBC its current priority list would prevent 99% of Covid deaths.

Professor Wei Shen Lim, the JCVI’s Covid-19 chairman, said: “As the single greatest risk of death from Covid-19 is older age, prioritisation is primarily based on age.”

A spokesperson added that while the JCVI “recognises that there may be an increased risk of transmission in prisons”, it would be “difficult to advise additional prioritisation of detainees above the wider population based on the potential increased risk of exposure in a detained setting alone”.