Impact case study database

Controlling HIV through evidence-based prevention and control strategies

HIV is among the deadliest and costliest global epidemics of the past half-century. Around 76 million people around the world have been infected, including 33 million people who have died. An estimated 38 million people currently live with HIV globally, including seven million who are unaware they have the infection (UNAIDS statistics). In the UK, about 100,000 people are living with HIV, with high concentrations among men who have sex with men and among black African populations [A]. Between 2000 and 2015, the HIV epidemic was estimated to cost the global economy over USD550 billion (Lancet 2018).

For more than a decade, researchers in Cambridge and at Public Health England (PHE) (and its predecessor organisations) have worked closely together to develop and deliver evidence-based approaches to support control strategies for HIV [1–5,7]. The approaches – involving intensification of prevention policies over time, informed by the estimates resulting from the Cambridge methods – have been associated with reductions in HIV transmission and in undiagnosed infections and late diagnoses. They have helped cut infection rates, with numbers of undiagnosed infections reduced by thousands in England alone.

Adopted by the UK and other governments, these approaches are essential to the tracking of HIV in populations, the development and implementation of strategies to reduce HIV spread, and the rapid evaluation of those strategies – all activities that are fundamental to disease control. Cambridge research has therefore contributed significantly to the remarkable improvements seen in the quality and quantity of life for thousands of HIV-infected individuals, to reductions in HIV transmission, and to savings in healthcare costs, placing the UK on track to eliminate transmission of HIV by 2030 [A].

Widespread adoption of Cambridge tools and estimates in the UK and internationally

Public Health England [A–C] has adopted the Cambridge techniques as the official methods for estimating HIV prevalence and incidence. Annual estimation of HIV prevalence in the UK has, since 2005, been based on the Cambridge Multi-Parameter Evidence Synthesis (MPES) approach. The Cambridge back-calculation method has provided incidence estimates since 2012. Both these estimates have been used by PHE to underpin its strategy, policy and practice recommendations [C], becoming an “essential component of PHE annual reports” and “the national yardstick to measure progress” in controlling HIV [B]. Guidelines from the National Institute for Health and Care Excellence (NICE) on increasing HIV testing uptake (2016) [D], and the British HIV Association UK National Guidelines for HIV Testing (2015, 2017 and 2020) [D], also endorse the Cambridge methods. Internationally, several European governments and agencies have adopted the Cambridge approaches, for example those using the recommended modelling tool of the European Centre for Disease Control, an agency of the European Union (including from Austria, Denmark, Finland, Greece, Malta, the Netherlands, Portugal, Bulgaria, Croatia, the Czech Republic, Slovakia, and Slovenia) [6,E].

A further far-reaching international impact has been through Fast-Track Cities [F], a global initiative involving hundreds of millions of people and 300 major cities around the world, led by the Joint United Nations Programme on HIV/AIDS (UNAIDS), the International Association of Providers of AIDS Care, and the United Nations Human Settlements Programme (UN-Habitat). Cambridge’s research plays a crucial role in this initiative by informing the targets and monitoring progress towards them, particularly in relation to UNAIDS’ 90-90-90 targets: that 90% of people living with HIV should know their HIV status; 90% of people with diagnosed HIV infection should receive antiretroviral therapy; and 90% of people receiving therapy should have sustained viral suppression. Analysis based on Cambridge methods has shown that the UK met the 90-90-90 target in 2016 [G], while London has exceeded the new 95-95-95 target [F].

Providing evidence for HIV prevention strategies

Evidence produced using tools developed by the Cambridge team has been crucial in establishing the effectiveness of HIV prevention strategies and providing the basis for policy intervention. Cambridge evidence was, for example, a key part of PHE’s written submission to the House of Commons Select Committee on Health and Social Care’s Report on Sexual Health in 2019 [H], used to support the approach of increasing HIV testing and early HIV treatment as prevention.

Since 2010, Cambridge estimates of undiagnosed HIV infections have underpinned multiple high-profile initiatives in the UK to increase testing. Examples include the Terrence Higgins Trust’s “It Starts with Me” campaign [I], the National HIV Prevention Programme for England [I], and the “Halve It” campaign, a coalition of organisations – including NICE, the Department of Health and Social Care, and the Local Government Association – working with the House of Commons All-Party Parliamentary Group on HIV/AIDS to halve the proportion of undiagnosed infections by 2020 [I].

Guided by information derived through Cambridge’s tools, these campaigns play a major role each year in public health initiatives, such as National HIV Testing Week. The success of these initiatives is evidenced by figures derived using Cambridge’s methods, which show a progressive decrease in the number of undiagnosed infections among gay and bisexual men, which has halved from around 8000 in 2008 to around 4000 in 2018 [A]. Regular application of the back-calculation approach has shown that the infection rate in gay and bisexual men has fallen steadily [A] (from around 2800 in 2012 to around 800 in 2018 – a reduction of over two thirds), with a steep fall in incidence in younger men.

There has also been a steady decline in the numbers of people receiving late diagnoses of HIV in the UK, decreasing from 1,861 in 2015 to 1,279 in 2019 [J]. Late (CD4 count <350 cells/mm³) and very late (CD4 count <200 cells/mm³) diagnosis of HIV is the most powerful predictor of mortality in infected people. The UK’s downward trend in late diagnoses [7] is therefore very important for health outcomes among those who are infected.

Using PHE data [K], it is possible to show what would have happened without intensified prevention after 2010. Assuming that the proportion of very late diagnoses remained constant over time at the level observed in 2010 (28%), an expected (counterfactual) number of very late diagnoses can be derived (Table 1). This suggests that around 1100 very late diagnoses were averted over the period 2014-18. From these figures, a cost saving of over GBP4 million per year can also be estimated. This cost is calculated as the difference between the respective yearly costs of GBP7.1 million and GBP3.1 million of very late and (comparatively) early diagnoses (Table 2). This offers an approximation of the economic impact of the policies fueled by Cambridge research.

Table 1. People aged 15 years and over diagnosed at very late stage. Data to end of December 2018. Source: [K].

Table 2. Annual costs for people living with HIV by CD4 strata and potential costs of illness for averted very late diagnoses of people living with HIV since 2014. Costs are taken from Beck et al. (https://doi.org/10.1371/journal.pone.0027830\) and are at 2008 prices. No deflation effect or temporal changes in costs are included.

Supporting bold, ambitious policies to eliminate HIV

The body of work from Cambridge and its collaborators, including PHE, has been highly influential in supporting policy-makers in the shift from a traditional containment strategy to a much bolder strategy of eliminating HIV altogether, particularly since the introduction of UNAIDS’ 90-90-90 target in 2016. Led by the evidence produced by Cambridge and the ability to monitor infections effectively, policies set out by the Department of Health and Social Care now focus on eliminating, not just controlling, HIV [A].

Cambridge work was used by the Department of Health and Social Care in its decision to establish an independent HIV Commission in 2019 [L], whose remit is to find ambitious and achievable ways to end new HIV transmissions and HIV-attributed deaths in England by 2030. In 2019, PHE cited Cambridge research, methods, tools and estimates [L] in its submission to the Commission.

The HIV Commission’s report, published in December 2020 [L], set an interim target of reducing transmission by 80% by 2025. The Cambridge back-calculation estimates were used in the report to show the decline in new infections. The importance of monitoring transmission by estimating incidence is highlighted in the report’s recommendation that “everyone serious about ending new transmissions must track our progress against estimated incidence of HIV, not new diagnoses alone.”

The report also made use of Cambridge estimates of undiagnosed prevalence from Public Health England’s latest annual report, including the key headline: “ The message from the HIV Commission is ‘test, test, test’. To find the estimated 5,900 undiagnosed people living with HIV in England, HIV testing must be normalised throughout the health service. Everyone should know their HIV status” [L].