They’ve been talking or it would appear. El Papa said:
I would say that this problem of Aids cannot be overcome merely with money, necessary though it is. If there is no human dimension, if Africans do not help [by responsible behaviour], the problem cannot be overcome by the distribution of prophylactics: on the contrary, they increase it. The solution must have two elements: firstly, bringing out the human dimension of sexuality, that is to say a spiritual and human renewal that would bring with it a new way of behaving towards others, and secondly, true friendship offered above all to those who are suffering, a willingness to make sacrifices and to practise self-denial, to be alongside the suffering.
If people have preferences for more sexual partners then they’ll weigh the costs of having more (the chance of getting infected with an STD) against those benefits. And if these preferences exist, Micheal Kremer says:
Surprisingly, the availability of an imperfect vaccine [wa: e.g. condoms] could reduce welfare, as well as increase prevalence. If the elasticity of the rate of partner change to the marginal probability of infection from an additional partner is greater than one, an individual who gains access to a partially effective vaccine will wind up with a higher risk of infection than without the vaccine. Although the individual benefits, others are made worse off, because prevalence in the pool of available partners will increase… The combined costs of the increased prevalence, plus the expense and side effects of the vaccine, could outweigh the benefits of a reduced risk of infection per partner and so introduction of an imperfect vaccine could make everybody worse off. This analysis suggests that one goal for empirical work should be to determine whether the elasticity of behavioral response to the probability of infection is less than or greater than one.
The Pope is saying people shouldn’t have such preferences. His wasn’t a statement about science (I think he knows condoms act as physical barriers to transmission to disease) its a statement about morals, aka optimal preferences. Does anyone know if that elasticity has been estimated?