The ASSA2008 model was released in March of 2011, and is the most recent version of the ASSA AIDS and Demographic model to be released. The most significant changes to the previous version of the model are greater estimates of the impact of antiretroviral treatment in recent years, as well as significant increases in levels in condom usage over the last decade.
There was a link to the model on the Actuarial Society’s website, however it has been taken down. There are instructions on how to obtain the model here:
I thought it would be interesting to point out that there are a number of shortcomings in the ASSA2008 model. These include:
1. many of the empirical assumptions about sexual behaviour have limited empirical basis
2. HIV transmission probabilities are calculated on an annual basis, making it impractical to allow for transmission dynamics that operate over short periods due to the high level of infectiousness during the first few months of HIV infection.
3. problems with calibration to some of the age-specific calibration targets, for example the model treats the life expectancy quite conservatively
4. the model does not allow for the effect of recent changes in guidelines for ART initiation in adults and children, and the effect these have on MTCT (mother to child transmission) rates
5. the model does not allow for new PMTCT (prevention of mother to child transmission) guidelines, particularly provision of extended NVP (nevirapine) prophylaxis to children breastfed by HIV+ mothers
6. the model does not allow for the effect of the campaign to promote male circumcision
7. the model does not allow for the effect of recent HIV testing campaign (12 million tested in 2010/11)
8. the model does not allow for new strategies that may be introduced in the future (microbicides, PrEP, earlier ART initiation)
A new ASSA model is being developed using the THEMBISA model and will address many of the shortcomings of the ASSA2008 model.