Could disease-modifying HIV vaccines cause population-level perversity?

doi:10.1016/S1473-3099(04)01148-X

The Lancet Infectious Diseases

Volume 4, Issue 10, October 2004, Pages 636-639

https://doi.org/10.1016/S1473-3099(04)01148-X Get rights and content

Summary

Most current candidate HIV vaccines seem to produce little protection against infection, but reduce viral load and slow the decline in CD4 lymphocyte numbers. Such disease-modifying vaccines could potentially provide important population-level benefits by reducing transmission, but could possibly also increase transmission. We address the following question: could disease-modifying HIV vaccines cause population-level perversity (ie, increase epidemic severity)? By analysing a mathematical model and defining a new quantity-the fitness ratio-we show that disease-modifying vacciness that provide only a low degree of protection against infection and/or generate high fitness ratios will have a high probability of making the epidemic worse. However, we show that if disease-modifying vaccines cause a 1·5 log₁₀ reduction in viral load (or greater) then perversity cannot occur (assuming risk behaviour does not increase). Finally, we determine threshold surfaces for risk behaviour change that determine the boundary between beneficial and perverse outcomes; the threshold surfaces are determined by the fitness ratio, the proportion of the population that are “successfully vaccinated”, and the degree of change of risk behaviour in unvaccinated infected individuals. We discuss the implications of our results for designing optimal vaccination control strategies.

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Citation Excerpt :
Partially effective vaccines have been of enduring scientific, clinical, and theoretical interest. For HIV, two decades of mathematical modeling studies suggest that partially effective vaccines, whether protective or therapeutic, can have a substantial impact on the HIV pandemic [3–15]. More recently, HIV epidemic models were used to predict the impact of a partially effective (protective) vaccine similar to RV144 in terms of VE and duration.
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Personal ViewCould disease-modifying HIV vaccines cause population-level perversity?

Summary

Vaccine

Trends Microbiol

Proc R Soc Lond B Biol Sci

The need for a global HIV vaccine enterprise

Science

HIV vaccines: a global perspective

Curr Mol Med

The challenges of an HIV vaccine enterprise

Science

A sound rationale needed for phase III HIV-1 vaccine trials

Science

Prospects for an AIDS vaccine

Nat Med

Personal View
Could disease-modifying HIV vaccines cause population-level perversity?