SEARCH: SouthEast Asian Research Collaborative in Hepatitis Viral hepatitis leads to greater mortality each year than HIV, TB or malaria. It ranks 7th amongst the leading causes of death worldwide. Unusually for an infectious disease, the numbers of deaths are distributed quite evenly between richer and poorer countries.   The challenge of tackling viral hepatitis has not yet been embraced by the global health community in the same way as HIV, TB and malaria which has been supported by the Global Fund which provides funding for treatments in countries otherwise unable to afford them. But more recently, a recognition of the relative importance of viral hepatitis has informed an ambitious WHO strategy launched for 2016-21.The WHO goals are to reduce deaths from viral hepatitis  by 10% by 2020 and 65% by 2030. To do this the ambition is to treat 3 million hepatitis C infected individuals by 2020 and 80% of eligible hepatitis C (HCV) infected individuals by 2030 (a global estimate of approximately 60 million individuals in the next 13 years). This will pose a major challenge, particularly to poorer countries with high burdens of infection, where costs of delivering treatment are prohibitive. Vietnam is ranked 9th amongst countries for deaths caused by viral hepatitis and has one of the highest mortality rates from hepatitis C in the world with an estimated 1 million individuals infected. It is also classifed as low-middle income by the World Bank. Current treatment rates in Vietnam are relatively low and use interferon containing therapies which involve long courses (24-48 weeks) including weekly injections, a high rates of side effects and offer cure rates in the region of 70%. However, there are now newly approved tablet treatment regimens (without interferon) of between 12 and 24 weeks. These courses of interferon-free direct acting antivirals (DAAs) are highly effective, with far fewer side effects. However, they are currently very expensive and these costs are the limiting factor for treatment in both richer and poorer countries at present. In addition, whilst 12 weeks of therapy represents great progress, many patients will struggle to take a full course.  Despite these facts, recommended therapies will overtreat a high proportion of patients, and over 80% of patients are likely to be curable with two thirds of the recommended treatment duration.  We lack are robust ways of predicting which patients these are and ensuring cure is achieved for the minimum price, inconvenience and toxicity. The proposed work aims to create a network and run studies to provide the data needed to inform how new treatments are used. This is particularly important in Vietnam as the type of hepatitis C circulating there is only rarely found in Europe and USA where most of the trials have been done to date. Genotype 6 hepatitis C, the most common genotype in Vietnam, has rarely been included in studies to date and may well differ in its responses to treatment compared to other genotypes. The Global Challenges Research Fund (GCRF) supports cutting-edge research to address challenges faced by developing countries. The fund addresses the UN sustainable development goals. It aims to maximise the impact of research and innovation to improve lives and opportunity in the developing world.