HIV

Given the extreme variability of the HIV virus, development of an effective HIV vaccine, especially one that is effective against all the various subtypes, remains extremely challenging. The first trial of a potential HIV vaccine was carried out in the US in 1987. Today, more than 30 vaccines have been tested in 80 phase I, phase II and phase III trials, in 19 countries (IAVI, 2005). There are currently no HIV vaccines licensed for use. Vaxgen's AIDSVAX, the only vaccine to undergo large-scale clinical efficacy trials, was not shown to be effective in protecting high-risk HIV-negative individuals from infection (Francis, 2003).

Development of an effective and safe HIV vaccine continues with a large scale Phase III study of 16,000 individuals in Thailand. Modest immunity was seen after 3 doses of the ALVAC HIV vaccine. Participants who received the series of inoculations plus a booster vaccine were 31% less likely to get HIV compared to those receiving placebos. While findings are modest, with 51 people contracting HIV in the vaccinated group versus 74 in the placebo, the study showed that HIV vaccine can be safe and possibly effective. (MHRP, 2009)

Global Alliance for Immunization Against AIDS (GAIA) is the only NGO dedicated to developing a vaccine with the needs of the developing world in mind. Through pursuing an epitopes-based vaccine, containing protein fragments that stimulate the immune system, GAIA is working to develop a vaccine that would be effective against all strains of HIV (GAIA, 2005).

At the XVI International AIDS Conference in August of 2006, the International AIDS Vaccine Initiative (IAVI) proposed new initiatives to speed up AIDS vaccine development. These new scientific and policy initiatives were established in the hope of finding better models for conducting AIDS vaccine research. This AIDS Vaccine Blueprint 2006 emphasizes the need for a better global research and development programs. These programs aim to assess vaccine candidates, discover prime scientific obstacles to the discovery and development of an HIV vaccine, analyze financial and political challenges in the search for an AIDS vaccine, and finally to recommend new strategies for overcoming these challenges. (EurekaAlert.org, Online 2006)

In 2011, the results of a multi-national clinical trail found that by simply enrolling in a program with a pre-exposure prophylaxis (PrEP) (tenofovir disoproxil fumarate [TDF] and emtricitabine [FTC]) component, men who have sex with men reduced the HIV aquivisition rate by 44%, while those particiapnts with >90% adhereance rates, saw a 73% decrease in HIV aquivisiton (MMWR, 2011). The Bangkok Tenofovir Study, a clinical trial which began in 2005, has released results showing that the use of PrEP is helpful in reducing the spread of HIV for injection drug users. In this study, when participants who adhered to  PrEP guidelines, reduced the HIV acquisition rate by 74%. (CDC, 2013).  Though numerous studies, it is being proven that PrEP programs greatly reduce the spread of HIV in vulnerable populations. 

Malaria

The task of developing a preventive vaccine for malaria is an extremely complex process for numerous reasons, the main one being P.falciparum's capability, through the development of multiple drug-resistance parasites, of evolutionary change.  

The Plasmodium Species has a very high rate of replication, much higher than that actually needed to ensure transmission in the parasite's life cycle. This enables pharmaceutical treatments that are effective at reducing the reproduction rate, but not halting it, to exert a high selection pressure, thus favoring the development of resistance.

The process of evolutionary change is one of the key considerations necessary when considering potential vaccine candidates. The development of resistance could cause a significant reduction in efficacy of any potential vaccine,thus rendering useless a carefully developed and effective treatment. (RTS,S Clinical Trials Partnership, 2012)

Bacille Calmette-Guérin (BCG)

The Bacille Calmette-Guérin (BCG) vaccine has existed for 80 years and is one of the most widely used of all current vaccines, reading >80%of neonates and infants in countries where it is part of the national childhood immunization programme. The BCG vaccine has a documented protective effect against meningitis and disseminated TB in children. It does not prevent primary infection and, more importantly, does not prevent reactivation of latent pulmonary infection, the principal source of bacillary spread in the community. The impact of BCG vaccination on transmission of Mtb is therefore limited.

The biological interaction between Mtb and the human host is complex and only partially understood. Recent advances in areas such as mycobacterial immunology and genomics have stimulated research on numerous new experimental vaccines, but it is unlikely that any of these urgently need vaccines will be available for routine use within the next few years. In the meantime, optimal utilization of BCG is encouraged. (WHO, 2013)