Mills J, Koelle K, Blower S; Australasian Society for HIV Medicine. Conference.
Annu Conf Australas Soc HIV Med. 1999 Dec 9-11; 11: 52 (abstract no. OR25).
NCHVR, Melbourne, Australia.
The need for a vaccine to abort the global HIV epidemic is clear. Based on experience with vaccines against other viral infections (polio & measles), a live attenuated HIV vaccine (LAHV) is likely to offer longstanding and superior protection against HIV infection, and thus would be useful in the global HIV control effort. However, all attenuated vaccines carry some risk of causing disease, and an LAHV might cause AIDS in a fraction of the recipients after an extended incubation period. To determine whether implementation of an imperfect LAHV would be of benefit, we modeled the impact of LAHV in a high prevalence country (Zimbabwe: approximately 25% prevalence) and a low prevalence country (Thailand: approximately 2.25% prevalence). The model was derived from that of Blower & McLean, Science 1994; 265:1451) with the following key parameters: all individuals at risk (age > or = 15 yrs) would be immunized over one year with follow-up immunization of all new at-risk individuals; immunization coverage of 80-95%; the LAHV has 50-95% protective efficacy; wild-type HIV causes AIDS in 50% in 7.5-10 years while LAHV causes AIDS in 1-10% in 25 years (triangular distribution, peak = 5%); dually-infected individuals progress to AIDS at a rate of 10%-100% of those infected with wild-type HIV alone. Modeling showed that in Zimbabwe (HIV prevalence approximately 25%) mass immunization with LAHV rapidly reduced the annual death rate from AIDS by 75% within 20 years and by 95% at the end of 40 years, with some possibility of eliminating wild-type HIV infection. Residual mortality (after year 20) was primarily attributable to the vaccine. In contrast, in Thailand (HIV prevalence approximately 2.25%) the vaccine invariably increased AIDS-related mortality, and deaths were virtually all LAHV-related. Overall vaccine effectiveness was thus dependent on that baseline prevalence of HIV infection, and sensitivity analysis showed that LAHV protective efficacy and degree of attenuation were also important determinants of outcome. This modeling study shows that an imperfect LAHV would provide substantial overall benefit in countries with a high prevalence of HIV infection, but would not be suitable for widespread use in low prevalence countries, where an LAHV having even a 1% incidence of AIDS in 25 years would have detrimental effects if given to the entire sexually-active population.
Publication Types:
Keywords:
- AIDS Vaccines
- Acquired Immunodeficiency Syndrome
- Disease Outbreaks
- HIV Infections
- HIV Seropositivity
- Health Services Needs and Demand
- Humans
- Immunization
- Incidence
- Prevalence
- Thailand
- Vaccines, Attenuated
- Virus Diseases
- Zimbabwe
Other ID:
UI: 102242676
From Meeting Abstracts