The potential global market size and public health value of an HIV-1 vaccine in a complex global market

Global and Regional Estimates for Subtype-Specific Therapeutic and Prophylactic HIV-1 Vaccines: A Modeling Study

Global HIV-1 genetic diversity forms a major obstacle to the development of an HIV vaccine. It may be necessary to employ subtype-specific HIV-1 vaccines in individual countries according to their HIV-1 subtype distribution. We estimated the global and regional need for subtype-specific HIV-1 vaccines. We took into account the proportions of different HIV-1 variants circulating in each country, the genetic composition of HIV-1 recombinants, and the different genome segments (gag, pol, env) that may be incorporated into vaccines. We modeled different scenarios according to whether countries would employ subtype-specific HIV-1 vaccines against (1) the most common subtype; (2) subtypes contributing more than 5% of HIV infections; or (3) all circulating subtypes. For therapeutic vaccines targeting the most common HIV-1 subtype in each country, 16.5 million doses of subtype C vaccine were estimated globally, followed by subtypes A (14.3 million) and B (4.2 million). A vaccine based on env required 2.6 million subtype E doses, and a vaccine based on pol required 4.8 million subtype G doses. For prophylactic vaccines targeting the most common HIV-1 subtype in each country, 1.9 billion doses of subtype A vaccine were estimated globally, followed by subtype C (1.1 billion) and subtype B (1.0 billion). A vaccine based on env required 1.2 billion subtype E doses, and a vaccine based on pol required 0.3 billion subtype G doses. If subtype-specific HIV-1 vaccines are also directed against less common subtypes in each country, vaccines targeting subtypes D, F, H, and K are also needed and would require up to five times more vaccine doses in total. We conclude that to provide global coverage, subtype-specific HIV-1 vaccines need to be directed against subtypes A, B, and C. Vaccines targeting env also need to include subtype E and those targeting pol need to include subtype G.

Global and regional molecular epidemiology of HIV-1, 1990-2015: a systematic review, global survey, and trend analysis

BACKGROUND

Global genetic diversity of HIV-1 is a major challenge to the development of HIV vaccines. We aimed to estimate the regional and global distribution of HIV-1 subtypes and recombinants during 1990-2015.

METHODS

We searched PubMed, EMBASE (Ovid), CINAHL (Ebscohost), and Global Health (Ovid) for HIV-1 subtyping studies published between Jan 1, 1990, and Dec 31, 2015. We collected additional unpublished HIV-1 subtyping data through a global survey. We included prevalence studies with HIV-1 subtyping data collected during 1990-2015. We grouped countries into 14 regions and analysed data for four time periods (1990-99, 2000-04, 2005-09, and 2010-15). The distribution of HIV-1 subtypes, circulating recombinant forms (CRFs), and unique recombinant forms (URFs) in individual countries was weighted according to the UNAIDS estimates of the number of people living with HIV (PLHIV) in each country to generate regional and global estimates of HIV-1 diversity in each time period. The primary outcome was the number of samples designated as HIV-1 subtypes A, B, C, D, F, G, H, J, K, CRFs, and URFs. The systematic review is registered with PROSPERO, number CRD42017067164.

FINDINGS

This systematic review and global survey yielded 2203 datasets with 383 519 samples from 116 countries in 1990-2015. Globally, subtype C accounted for 46·6% (16 280 897/34 921 639 of PLHIV) of all HIV-1 infections in 2010-15. Subtype B was responsible for 12·1% (4 235 299/34 921 639) of infections, followed by subtype A (10·3%; 3 587 003/34 921 639), CRF02_AG (7·7%; 2 705 110/34 921 639), CRF01_AE (5·3%; 1 840 982/34 921 639), subtype G (4·6%; 1 591 276/34 921 639), and subtype D (2·7%; 926 255/34 921 639). Subtypes F, H, J, and K combined accounted for 0·9% (311 332/34 921 639) of infections. Other CRFs accounted for 3·7% (1 309 082/34 921 639), bringing the proportion of all CRFs to 16·7% (5 844 113/34 921 639). URFs constituted 6·1% (2 134 405/34 921 639), resulting in recombinants accounting for 22·8% (7 978 517/34 921 639) of all global HIV-1 infections. The distribution of HIV-1 subtypes and recombinants changed over time in countries, regions, and globally. At a global level during 2005-15, subtype B increased, subtypes A and D were stable, and subtypes C and G and CRF02_AG decreased. CRF01_AE, other CRFs, and URFs increased, leading to a consistent increase in the global proportion of recombinants over time.

INTERPRETATION

Global and regional HIV diversity is complex and evolving, and is a major challenge to HIV vaccine development. Surveillance of the global molecular epidemiology of HIV-1 remains crucial for the design, testing, and implementation of HIV vaccines.

FUNDING

None.

Challenges for nationwide vaccine delivery in African countries

Vaccines are very effective in providing individual and community (herd) immunity against a range of diseases. In addition to protection against a range of diseases, vaccines also have social and economic benefits. However, for vaccines to be effective, routine immunization programmes must be undertaken regularly to ensure individual and community protection. Nonetheless, in many countries in Africa, vaccination coverage is low because governments struggle to deliver vaccines to the most remote areas, thus contributing to constant outbreaks of various vaccine-preventable diseases. African governments fail to deliver vaccines to a significant percentage of the target population due to many issues in key areas such as policy setting, programme management and financing, supply chain, global vaccine market, research and development of vaccines. This review gives an overview of the causes of these issues and what is currently being done to address them. This review will discuss the role of philanthropic organisations such as the Bill and Melinda Gates Foundation and global partnerships such as the global alliance for vaccines and immunizations in the development, purchase and delivery of vaccines.

The current challenges for vaccine development

Vaccine development has played a hugely important role in combating infectious disease. Despite this success, there is still a great need for new vaccines and these are emerging far more slowly than we would wish. Despite the massive expansion in understanding of immune responses to infection, research is often hindered by a lack of understanding of the immune responses required specifically for protection, or by a lack of approved adjuvants and delivery systems to induce the required responses. In addition, the financial commitment required to license new vaccines is significant, and the more lucrative markets are often not those with the greatest need. In this review, we discuss many of the hurdles that new vaccines must overcome in order to reduce morbidity and mortality, and some of the initiatives that are being attempted to supply new vaccines to those that need them most.