The number of prisoners suspected to have been infected by coronavirus is more than five times the number of confirmed cases, public health experts have revealed, amid “cautious optimism” that “explosive” outbreaks in jails have been averted. The Ministry of Justice published analysis by Public Health England saying there was evidence of successful containment of the outbreak in prisons. But the paper, written by Dr Éamonn O’Moore, the national lead for health and justice at PHE, said that “while the current situation is cause for cautious optimism, significant threat levels remain”. PHE data showed there had been 304 laboratory-confirmed cases of Covid-19 in prisoners in England and Wales at the last count, as well as 1,783 “possible/probable” cases. The most up-to-date figures showed there were 324 confirmed cases among prisoners as at 5pm on Sunday. The deaths of 15 prisoners and five prison staff have been directly or indirectly linked to coronavirus. Prison staff have access to testing but the paper states that testing for prisoners has been “limited and variable”. The research shows the most likely source of an outbreak is fresh arrivals into prisons, and as a result Moore suggests that specialist accommodation for new receptions or transfers and shielding units to protect the most vulnerable will be required at least to the end of March 2021. This would limit deaths to 100 over the period, the modelling suggests. There are 81,500 prisoners in England and Wales. Moore writes: “While the level of prevalent infection in the community will likely wane over the summer months as the pandemic wave plateaus and then decreases, there will still be circulating Covid-19 virus and epidemiologists predict a risk of a second wave or even a third wave before we have a vaccine. “These are important considerations for policymakers in determining how to lift current restrictions on normal life in the community but will also be a consideration for prisons going forward for the rest of this year.” It is understood observations made in the paper are in part behind the reasons why so few prisoners have been released early under emergency measures announced by the government on 4 April. The Ministry of Justice said it would free up to 4,000 prisoners who were within two months of their release date and had passed a risk assessment. But on Monday the justice secretary, Robert Buckland, revealed that only 33 prisoners had been released, including pregnant prisoners. Buckland told the House of Commons there were positive signs that the approach in prisons was working, although he cautioned: “We are not out of the woods yet.” PHE and the prison service have estimated that a restrictive regime introduced in prisons as well as reduction in prison transfers has reduced contacts across the prison estate by up to 50% compared with the pre-pandemic regime. Prison reform campaigners continue to call for more prisoners to be released, warning that “the clock is ticking”.