COVID-19 vaccine policy for prisoners has been in the headlines across the USA and the UK. Discordant strategies exist, ranging from no vaccination, to vaccination equivalent to people in the community, to higher prioritisation for people in prison. Prisons are dangerous hotspots for acquiring SARS-CoV-2, and individuals who return to the community could unwittingly transmit the virus. In the USA alone, 372 583 prisoners have had COVID-19, with 2359 deaths, according to the Marshall Project. The COVID-19 pandemic has highlighted the need to address racial and social inequalities globally, but the same lens is often not applied to prison-related policies. Prison health systems remain a weak link in public health preparedness, racial and social justice, and human rights. Globally, 10·74 million people were in penal institutions as of 2018, either as pretrial detainees, on remand, or having been convicted and sentenced. Since 2000, the number of people in prison has grown by 24%, with a worrying rise in the female prison population, which has outpaced the growth rate among males. The USA still has the most people in prison, with 2·1 million, and has the highest rate of prisoners relative to the population. Previous publications in The Lancet have underscored the serious gaps in care and follow-up for prisoners, both inside prison walls and in the community. Certainly before COVID-19, prisoners faced a higher burden of poverty, discrimination, disease, mental health issues, and substance use disorders. Insufficient follow-up for prevention and treatment of conditions can also be affected by incompatible health data management systems for prisons and community health providers. Each year, millions of people cycle in and out of prisons. It stands to reason that the barbed wire and walls that surround prisons are not an N95-style barrier against disease and inequality. The UN has called for countries to embrace a health systems approach, where prisons are integrated within community health services. In 2015, the UN Standard Minimum Rules for the Treatment of Prisoners (the Nelson Mandela Rules) called for prison health systems to be equivalent to what is provided in the country as a whole, while ensuring that risks to health are minimised. This stipulation includes women prisoners when giving birth, and their children. UN guidance also calls for community prevention of health conditions, including for mental health and substance use to be addressed early, owing to the risk of incarceration for people with such conditions. Several areas could be prioritised for legal and policy reform to improve prison health. Since 2014, WHO has recommended that countries review their laws and decriminalise behaviours such as drug use, sex work, and engaging in same-sex sexual activity, including for those with non-conforming gender identities. 69 countries still criminalise same-sex sexual behaviour (about half are Commonwealth countries with archaic colonial era laws). In Asia, over 400 000 people are detained in forced drug rehabilitation and compulsory detention centres, a figure that does not include those in prison. Such laws should be repealed, which will also reduce societal stigma as well as racial and social inequalities that can disproportionately affect the most vulnerable. Detaining people unnecessarily is unjustifiable from a human rights perspective and it is bad for public health. A strong accountability mechanism for the Nelson Mandela Rules is also needed so that progress can be monitored and poor compliance addressed. Countries could also close the jurisdiction chasm between ministries of health (which provide health recommendations) and ministries of justice (which oversee prisons and prison health). Fortunately, there has been some progress on prison health reform. COVID-19 has encouraged some countries to look at overcrowding and to pay more attention to prisoners with high-risk comorbidities, such as diabetes, obesity, and cardiovascular disease. The pandemic has also encouraged discussion on vaccination in prisons, which all otherwise eligible prisoners should receive. In Europe, England and Finland have transferred the governance of prison health from the justice ministry to the health ministry. In the USA, President Joe Biden has abolished federal contracts with privately operated, for profit, criminal detention facilities. Humane and evidence-based prison health systems with community links will improve public health within and outside prison walls, both for COVID-19 and other health issues. Such an approach is key to the pursuit of a just and equitable society. As Nelson Mandela said, “A nation should not be judged by how it treats its highest citizens, but its lowest ones.” For more on contrasting COVID-19 vaccination strategies in prisons see https://www.texastribune.org/2021/02/03/texas-prisons-coronavirus-vaccine/, https://news.sky.com/story/covid-19-vaccine-rollout-in-english-prisons-to-begin-today-12201902, and https://www.oregonlive.com/coronavirus/2021/02/coronavirus-in-oregon-judge-orders-inmates-be-prioritized-for-covid-19-vaccines-23-new-deaths-reported-statewide.html For the Marshall Project see https://www.themarshallproject.org/records/8793-covid-19 For more on the world prison population see https://www.prisonstudies.org/sites/default/files/resources/downloads/wppl_12.pdf For more on the increase in the female prison population see https://www.prisonstudies.org/news/world-female-imprisonment-list-fourth-edition For WHO guidance for prisons see https://www.who.int/topics/prisons/en/ For more on criminalisation of same-sex sexual behavior see https://ilga.org/downloads/ILGA_World_State_Sponsored_Homophobia_report_global_legislation_overview_update_December_2020.pdf For more on the governance of prison health see https://apps.who.int/iris/bitstream/handle/10665/336214/WHO-EURO-2020-1268-41018-55685-eng.pdf © 2021 Yuri Cortez/AFP/Getty Images 2021 Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. 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