Sexually transmitted infections (STIs)

Overview

Although most STIs are not life-threatening, they can pose significant health risks without proper diagnosis and timely treatment. This includes a litany of long-term complications disproportionately felt by women, including pelvic inflammatory disease, ectopic pregnancy, cancers of the female reproductive system and infertility. Many STIs also lead to increased susceptibility to HIV. Globally, more than one million STIs are acquired daily among people aged 15–49, with most cases presenting without symptoms. This is a problem, as it often results in delayed diagnosis and treatment, particularly in LMICs where access to timely and comprehensive STI care can be limited. Critically, some previously treatable STIs, such as gonorrhoea, are now showing widespread antibiotic resistance, posing serious public health challenges globally. There is a pressing need for new diagnostics, drugs, vaccines and other therapeutics to keep ahead of the curve on antimicrobial resistance and find prevention and treatment approaches for a range of STIs.  

Unmet needs

Current R&D efforts focus on addressing diagnostic, prevention and treatment gaps. The development of rapid, affordable point-of-care diagnostic tests is seen as critical for improving early detection, ideally for multiple STIs concurrently, particularly in LMIC settings where higher-tech molecular diagnostic tests (like those used for COVID-19) are too costly or inaccessible. Antimicrobial resistance is a growing concern, particularly for gonorrhoea, Mycoplasma genitalium and trichomoniasis, highlighting the urgent need for novel therapies to address these infections. However, besides gonorrhoea, the drug pipeline is limited to candidates in early-stage development. Diagnostics to better guide treatment and avoid increased resistance are also needed. Vaccine (preventive and therapeutic) and microbicide development could also provide important tools for containing the growth of antimicrobial resistance. Despite ongoing research, though, there are currently no approved vaccines for chlamydia, HSV-2, HTLV-1, syphilis or gonorrhoea, and a range of other lesser known STIs. Antivirals for HSV-2 - genital herpes – also have limited efficacy, greatly increasing the potential benefits from new prophylactic and therapeutic vaccines. Some promising candidates in this domain include Moderna’s mRNA-1608, with an ongoing Phase I/II clinical trial scheduled to complete in 2025 and BioNTech’s BNT163, which is currently undergoing Phase I investigation.

Funding

Overall funding for STI R&D has more than doubled since we began collecting data in 2018, rising from $96m to $217m. A near-tenfold increase in industry funding accounts for most of the net growth. The Gates Foundation – which began its (non-HIV) STI funding only in 2021 alongside the establishment of its Women’s Health Innovation Team – providing another $11m. This overall growth partly reflects the growing burden of some STIs in high income countries, and comes amid the backdrop of growing concerns about the rise of antimicrobial resistance (AMR) in STIs. Gonorrhoea, alongside two lesser known pathogens included in our ‘Other STIs’ category, has been identified by the WHO as a priority AMR risk and, partly as a result, accounts for 30% of the long-term growth in STI R&D.

The largest area of growth in STI funding in 2023 was funding for herpes simplex virus 2 (HSV) R&D, which rebounded from a slight drop in 2022 to reach $84m in 2023. However nearly half this growth in 2023 was from a new survey participant for a project which likely began a year or two earlier. So while our long-term growth estimate – $66m or 364% since 2018 – is likely accurate, the 2023 increase, specifically, is a little overstated.

HSV-2 has gone from receiving less than 20% of STI funding in 2018 and 2019 to almost 40% in 2023. This is largely a result of rising industry funding for biologics and (to a lesser extent) vaccines – mostly therapeutic vaccines – as a result of their huge commercial potential, particularly in HICs. Private sector funding for HSV-2 rose from $11m in 2018 to more than $76m, leaving industry responsible for 90% of the 2023 total. Funding from the US NIH, the only other major contributor to HSV-2, has remained relatively stable at around $8m. Like industry, the NIH focused on vaccines, including a new $0.8m grant in 2023 for early-stage mRNA vaccine development.

Mirroring the overall trend for STIs, funding for gonorrhoea dipped slightly in 2022 (by $9.4m, -14%) before rebounding strongly in 2023. Both rise and fall were due to a temporary lull in industry vaccine funding and big cyclical shifts in funding from CARB-X – a global partnership for AMR-related R&D. CARB-X provided several large, up-front disbursements for drug R&D – totalling $14m – in 2019, before shifting its focus to vaccines in 2023, along with a significant amount of AMR gonorrhoea-relevant multi-STI diagnostic funding covered under ‘multiple STIs’, below.

While funding from both industry and CARB-X returned to around 2021 levels in 2023, the record high in gonorrhoea funding was driven by $7m for basic research from the Gates Foundation. This was its first ever reported contribution to gonorrhoea R&D, for an epidemiological proof-of-concept study on gonorrhoea vaccine uptake among adolescent girls and young women in South Africa.

Despite the Gates Foundations’ boost to basic research, most gonorrhoea funding in 2023 still went to preventive vaccines, as was the case in each of the previous three years. Much of the remaining funding for gonorrhoea R&D was provided by the NIH, which – despite a drop in its vaccine funding – maintained its position as the largest overall funder of gonorrhoea R&D.

Funding for chlamydia remained mostly unchanged at $28m in 2023, although this was up more than $16m (145%) from its 2018 level, following rapid growth in 2019-2021. The majority of the funding in 2023, and most of the growth since 2018, came from either the NIH (with $15m in 2023 funding, up $4.3m from 2018) or industry ($11m, up from nothing in 2018), with NIH funding focusing on basic research and industry on vaccines. After earlier falls in diagnostics funding from the NIH and the German BMBF, this left overall funding in 2023 still split relatively evenly between basic research and vaccines.

The third largest contributor to chlamydia R&D in both 2022 and 2023 was the Indian ICMR – which was also the only substantial LMIC contribution to STI R&D. The ICMR’s funding averaged a little under $1.2m a year since it began in 2021. This was more than ten times the next largest funder – the Canadian CIHR – underlining how little interest there remains in chlamydia R&D outside the NIH and industry.

Funding for syphilis declined by 21% ($2.5m) from 2022's record high to $9.4m – or less than 5% of overall STI R&D. Even after this decline, though, 2023 syphilis funding was still more than four times its 2018 total.

Both the 2022 rise and the 2023 fall were mostly due to a much-needed spike in early-stage vaccine funding from Open Philanthropy, which left it responsible for two-fifths of global syphilis R&D in 2022. The decline in Open Philanthropy’s 2023 funding was partly offset by a rebound in contributions from the NIH and further growth in funding from the Gates Foundation. These three organisations – Open Philanthropy, Gates and the NIH – have driven the overall growth in syphilis funding, increasing their combined funding from just $2.2m in 2018 (when funding from Gates and Open Philanthropy had yet to begin) to a combined $8.7m in 2023. This 2023 total included a record $3.6m from the NIH, mostly for vaccine-oriented basic research.

Human T-lymphotropic virus 1 (HTLV-1) is the only individual STI to have seen its funding decline since 2018, dropping by a further $0.9m to $6.0m in 2023. This long-term decline is essentially all due to reduced basic research funding from the NIH, which has dropped by 41% ($3.4m) since 2018. Both the 2023 drop and the long-term fall were worsened by a 2023 cessation in funding from Wellcome, which had provided at least half a million dollars each year prior, most of it for basic research.

These declines contributed to a $0.5m drop in basic research, to a record low $4.8m. Despite this, basic research continued to account for more than 70% of overall funding, as it has every year, as researchers attempt to find out more about the virus’ little-understood pathology and epidemiology.

The only area with meaningful long-term growth has been HTLV-1 vaccine R&D, which rose from less than $18k in 2018 to $0.9m in 2023, thanks to new funding from the NIH. Though the amounts remain small, the $2.5m spent on HTLV-1 vaccines over the previous three years represents nearly forty times the total over the first three years of the survey.

The Japan Society for the Promotion of Science, whose funding reflects the unusually high incidence of HTLV-1 in Japan, has provided an average of $0.2m a year since 2018, and was the only supporter of HTLV-1 vaccine R&D until the NIH funding began in 2021.

Funding for R&D addressing multiple STIs was mostly unchanged at $12m in 2023, down by just under $2.4m (-16%) from 2018. The long-term downward trend partly reflects a highly variable stream of lump-sum diagnostics funding from CARB-X, much of which arrived in 2020 following a call for proposals for diagnostics targeting gonorrhoea alongside other STIs. CARB-X funding will likely prove to have rebound sharply in 2024, after it launched another call for gonorrhoea products. This most recent, 2024 round of CARB-X funding included $1.8m for a recently approved at-home test for chlamydia, gonorrhoea and trichomoniasis.

Multiple STI funding from industry, which has focused exclusively on diagnostics, has gradually grown from nothing at all between prior to 2021 to $6.5m in 2023, leaving industry the largest funder in a down year for CARB-X. Conversely, contributions from the NIH – especially their funding for diagnostics – have instead trended downwards, falling by two-thirds ($3.9m) since 2018.

Overall multiple STI R&D funding remains focused on diagnostics, which received more than three-quarters of 2023 funding. This reflects the global need for products which can be used to diagnose multiple STIs in a single application, especially in low-resource settings.

Funding for the Other STIs category, which includes AMR-risk STIs such as trichomoniasis and M. genitalium, narrowly surpassed its previous 2021 high of $4.1m to reach a peak of $4.3m in 2023, though this was still just 2% of STI spending.

Funding for basic research plays a key role in these often poorly understood diseases and jumped to $2.4m (up $2.2m, 1270%) thanks to the US NIH and the Gates Foundation. Industry did not provide any Other STI funding in 2023, after contributing a total of $2.8m for M. genitalium diagnostics between 2021 and 2022.

Funding for STIs