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Dr. Leonard L. Maboko

EXECUTIVE DIRECTOR

PROGRESS IN HIV VACCINE DEVELOPMENT AND TESTING IN TANZANIA

1. Introduction
Tanzania is one of sub-Saharan African countries which are devastated by the HIV/AIDS epidemic. The epidemic was recognized in Tanzania in 1983 and by December 1986 all regions had reported at least a case. Women are affected more than men at a ratio of 1.22 i.e. where 122 women are infected, 100 men are infected. This gender difference in HIV/AIDS infection is largely due to biological and socioeconomic factors. Urban residents have higher risk of HIV infection than rural residents. According to results from the recent Tanzania HIV/AIDS Indicator survey, HIV prevalence among adults aged 15  - 49 years is 7%. The prevalence among women and men of that age group is 7.7% and 6.3% respectively. Applying these data to estimate the year 2003/2004 burden of HIV infection in Tanzania mainland, it is realized that a total of 1,077,040 adult (460,739 males and 616,301 females) aged 15  - 49 years are living with HIV in Tanzania. Of these, 215,408 (20%) (92,148 males and 123,260 females) are estimated to have AIDS, and therefore need life prolonging antiretroviral (ARV) drugs.

2. Need for HIV vaccine in Tanzania
It is widely believed that effective control of HIV infection will ultimately need development of a potent vaccine to complement other interventions of proven efficacy. For this reason human HIV vaccine trials were initiated as early as 1987, and since then several different HIV vaccine candidates have been tested for safety (Phase I) and ability to elicit immune response (Phase II) clinical trials globally. Most HIV vaccine trials have, however, been done in the USA and Europe and very few in Africa where HIV infection rates and the burden of disease are the highest. Among all the HIV vaccine candidates, two (VAXGEN vaccines) have gone through phase III trial both in the USA and in Thailand. Although safe, the candidate vaccines failed to confer protective immunity among trial participants. In Africa, only 4 countries including Uganda, Kenya, S. Africa and Botswana have conducted phase I and or II vaccine trials to date. Other African countries (Cameroon, Cote d voire, Malawi, Nigeria, Rwanda and Tanzania) have initiated plans for HIV vaccine trials with international partners. Various other African countries are at different levels of planning to conduct HIV vaccine trials.

The continuing high rates of new HIV infections in Tanzania emphasize the need for additional biomedical tools such as preventive HIV vaccines and microbicides which are simple, affordable and effective to complement ongoing efforts. It is clear that development and availability of a safe and effective HIV vaccine offers the best and most cost-effective strategy for prevention of new HIV infections and will contribute significantly to efforts in poverty alleviation.

An AIDS vaccine is urgently required in Tanzania for the following reasons:

  • AIDS has serious and devastating social, economic, health and security consequences and is threatening our own existence in the country.
  • Private sector market driven HIV vaccine research and development is not attractive to making HIV vaccines relevant to developing countries including Africa and special initiatives are needed to support vaccine development for use in developing countries including Tanzania.
  • Treatment, care and support for HIV/AIDS including access to ART, is not yet readily available to most affected individuals in Tanzania and will not suffice in HIV prevention and control.

3. The potential role of an effective vaccine in the control of the HIV epidemic
The current responses to the epidemic include preventive education and behavior change strategies as well as voluntary counseling and testing, treatment, care and support interventions. These measures have led to reduction in the prevalence and incidence of HIV in some populations in Tanzania as well as mitigating the impact of the epidemic. However, there is a need for more effective measures to further control the epidemic. An effective vaccine against HIV is one such intervention that is likely to have the ultimate effect of controlling the epidemic. This strong optimism is supported by the historical precedence of effective prevention and control of several infectious diseases through vaccination.

4. The current situation of HIV vaccine development and trials in Tanzania

4.1 Ongoing research activities
There are several on going studies for the development of HIV vaccine in Tanzania. One of these, the HIV immunogenicity study (HIVIS) started in 2002 and was supposed to end in November 2005. The main objective of this study was to investigate ability of vaccines to elicit immune response and to optimize the immunization schedule. The study also aims at capacity building in terms of development of expertise and establishment of necessary infrastructure to study HIV-1 vaccines in Tanzania.

This Phase I/II vaccine study in Tanzania is embodied in a collaborative study involving scientists from Muhimbili University of Health and Allied Sciences (MUHAS), Tanzania and from Sweden, the USA, Germany and South Africa which also includes laboratory capacity building. Within this framework a TANSWED HIV programme study has extensively studied a cohort of police officers in Dar es Salaam, which is earmarked for the phase I/II trial.

In Mbeya the Ludwig-Maximillian University, Germany in collaboration with scientists from Tanzania, is coordinating a similar DNA HIV-I subtypes vaccine study. The University of Cape Town, South Africa, under the South African Vaccine Initiative (SAAVI) is also collaborating with the Mbeya site and is mainly dealing with sequencing of the HIV-1 strains in Mbeya as an important preparatory step towards HIV-I vaccine development and testing in Tanzania. The Walter Reed Army Institute of Research (WRAIR), USA has multiple HIV vaccine trial sites including Mbeya in Tanzania, Uganda and Kenya, using the DNA prime MVA boost strategy.

4.2. The National HIV Vaccine Strategic Framework
Recently, the Ministry of Health and Social Welfare released the National HIV Vaccine Strategic Framework which was developed through collaboration with Tanzania HIV vaccine research institutions, WHO-UNAIDS and the African AIDS Vaccine Programme (AAVP). The purpose of the framework is to provide guidance to Government sectors and scientific groups in Tanzania working with international and national stakeholders, civil societies and communities and NGOs in the development and evaluation of candidate HIV vaccines relevant to Tanzania.

Participation in vaccine trials involves collaboration between various national and international players and stakeholders. A national strategic framework provides a medium for expressing a consensus position on the country’s strategies for development and evaluation of candidate vaccines. The necessary research and related activities will stimulate multi-disciplinary teamwork with stringent regulatory guidelines and control. By providing clear rules on regulatory approval, scientific and ethical reviews, bio-safety and monitoring guidelines, such a plan is likely to attract the vaccine industry, research collaborators and funding agencies with candidate vaccine products to assist the building of local infrastructure and facilitate the transfer of knowledge and technology. The guidance will be used by authorities responsible for the approval, coordination and supervision of conducting HIV vaccine trials in the country and provide a useful resource to members of scientific and ethics review committees as well as to national drug regulatory and bio-safety authorities in regulating HIV vaccine development and trials in the country

5. Current efforts to scale up development of HIV vaccine candidates and trials in Tanzania

5.1 Role of the Government, Political Leaders and Policy Makers
Political support is essential for the success of any HIV vaccine development. The Government can provide an enabling environment for the researchers, their collaborators and funding agencies. It is important for political leaders at all levels from top down to the grass-root levels, cultural and religious leaders to be adequately informed and consulted at all stages of vaccine development. Political leaders play a critical role in communicating the relevant messages to the populations as well as in mobilizing the community for participation in national HIV vaccine development.

It is also important to realize that early vaccines may not be 100% effective and must therefore complement, not displace ongoing prevention, control, treatment, care and support programs. Moreover vaccine development is a long-term goal, which requires long-term financial, scientific, political, societal and resources commitment over many years. It is also equally important to ensure that the public does not receive mixed messages in this regard and emphasis need to be placed on the fact that prevention is still an integral part of the strategy of combating HIV/AIDS. In Tanzania, HIV vaccine development and testing is fully supported by the government as enunciated in the National HIV/AIDS Policy and National HIV Vaccine Strategic Framework.

5.2 The importance of HIV vaccine trials in Tanzania
Due to the large number of new infections, an effective vaccine would eventually benefit Tanzania greatly. However, the high variability of HIV in Tanzania necessitates testing of vaccine candidates in different areas of the country where different subtypes are prevalent. It is therefore necessary to address the issues of HIV strain diversity as well as evaluate if different routes of transmission or host genetic background may influence vaccine-induced protection. In addition licensing of HIV vaccines for use in the country by the regulatory Tanzania food and drug administration (TFDA) body will require prior trials in Tanzania. Discovery of an HIV vaccine in other countries is likely to take a long time to trickle down to Tanzania and may not be effective for the viral sub-types, which are prevalent in the country. Trials will therefore provide opportunities to study diverse population groups in endemic areas, against a multiplicity of HIV subtypes found in the country. Lastly the infrastructure and capacity developed for vaccine research will serve for other interventions such as microbicides research, provision of ART and other priority infectious diseases.

Conclusion
Despite very early global initiatives for the development of HIV vaccines, to date no effective vaccine has been developed and very few studies have been conducted in Africa including Tanzania. In realization that vaccine development will highly contribute to controlling the HIV epidemic, vaccine studies have been initiated in Tanzania, mostly aiming at phase I/II trials. It is important for the country to involve itself in vaccine trials due to HIV antigenic diversity. Vaccine development is however, a long-term commitment, which requires inputs from several partners, stakeholders and sectors including the government and policy makers.

There is a strong need for countries in Africa to develop common policies and strategies for the conduct of vaccine trials. Such policies and strategies need to address the unique socio-cultural and economic factors in Africa. A common approach in this endeavor will also place countries in Africa in a better negotiation position to access a vaccine of proven efficacy in the event that one becomes available as an outcome of multi-center clinical HIV vaccine trial.

The fight against HIV/AIDS
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