of HIV vaccine will depend on the context in which it is used, the characteristics of the vaccine, the strategy of administration and how people respond to it use. In a multisite study using data from Zimbabwe, Uganda and Thailand (1), it was shown that for a vaccine that was 50% efficacious, with 10 years protection and 65% coverage, the incidence of HIV wuld be reduced by 25% in Zimbabwe in adults 15-49 years of age. It is also known that the type of protection (degree or take) could make a large difference to the impact. On further analyzing Zimbabwean data with respect to type of protection, it was shown that using a vaccine with 50% efficacy , after 5 years, with 65% coverage, HIV incidence would 32% lower than without the vaccine using either take or degree protection. This is a huge impact if it can be achieved in real life. On further modeling using vaccines of different levels of efficacy, is was shown that at 95% efficacy, vaccine programs can nearly extinguish the epidemic in Zimbabwe. Clearly the model showed that the better the efficacy the higher the impact. The duration of protection conferred by the vaccine is also of importance. The longer the protection, the higher the impact data showed. However the strategy of revaccination may increase costs but has the same impact as vaccines with long duration of protection. Thus it would appear that a vaccine that is highly efficacious, with life long protection and with wide coverage and given to adults would have a major impact on childhood HIV infection rates since the 99% of paediatric HIV infection is acquired from mother to baby in our population. A vaccine of low efficacy, short duration of protection will have no impact and would give false assurance and even increase risky behaviours, 9