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On the potential impacts of male circumcision on Africa’s HIV
epidemics from modelling and simulation
About male circumcision, the main question remains: What effects
could the scale-up of male circumcision [MC] have on the population-level
dynamics of the HIV epidemics in sub-Saharan Africa? Efforts to answer
this question have taken the form of mathematical modelling and simulation
exercises 1-4, inevitably involving considerable uncertainty.
Karim et al. 5 identified surgery as a key point of uncertainty.
Assuring the same quality than in trials, by using trained medical team
for surgery and counselling, with the same standard of care, particularly
the respect of healing period, are central points for implementing with
success circumcision program. Although we agree that the way to integrate
circumcision program in existing sexual health services may be “the
biggest challenge”, other points of uncertainty need to be raised once the
surgery is done.
The potential behavioral impacts of MC constitutes another
significant source of uncertainty. Now the susceptibility-reducing effect
of MC is quickly becoming common knowledge in many parts of sub-Saharan
Africa, men are likely to receive a very different message about the
protective effects of MC. Under these circumstances, circumcised men may
decrease their condom use or engage in riskier behaviour because they
perceive that MC provides full or partial protection against HIV. Another
reason to expect some impact of MC on sexual behavior involves changes in
the balance of power between women and men. MC could make it more
difficult for women to bargain for condom use with their male partners.
Circumcised men will be in a stronger position to argue that it is
unnecessary for them to use condoms since they have already taken dramatic
steps to reduce their risk of infection. The uncertainty here involves the
nature and magnitude of these behavioral impacts, and the population-level
consequences thereof. Gray and colleagues 1 found that a 25% increase in
the number of sexual partners could completely wipe out the population-
level effects of MC, and that a larger increase could cause HIV epidemics
to become substantially more severe than the baseline scenario.
Another consideration with respect to existing simulation models
involves uncertainty in estimates of current MC and HIV prevalence levels.
The prevalence of MC used in some simulation models is based upon data
that are several decades old and therefore must be considered with
caution. Moreover, using an average level of prevalence for a specific
country does not take account of the diversity that exists according to
ethnicities and geographical regions. Similarly, for many countries in sub
-Saharan Africa, historical and current estimates of HIV prevalence may be
inaccurate. This is especially true for countries that have relied upon a
small number of sentinel surveillance sites (e.g., antenatal clinics
attendees in urban areas) to obtain estimates of national HIV prevalence.
For many countries, estimates have improved in recent years as a result of
more systematic efforts to estimate national HIV prevalence levels, but
this progress has not been uniform. Clearly, inaccurate figures on current
levels of MC or HIV prevalence may lead to an incorrect baseline and
misleading conclusions for simulation studies.
Finally, leaving aside the simulation models, country level estimates
of current MC and HIV prevalence provide a sobering reminder that other
powerful forces besides MC are at work, such as social, cultural,
historical, religious or sexual factors. Consider for example Rwanda and
Zimbabwe in which it is estimated than 10% of men are circumcised 4. In
Rwanda, HIV prevalence is only 5% and in Zimbabwe it is 25% 4. These
figures strongly suggest that the association between MC prevalence and
the course of HIV epidemics is far from perfect. MC may be an important
tool for reducing the spread of HIV in some parts of sub-Saharan Africa.
But we must not allow our enthusiasm for this intervention to prevent us
from continuing to develop the fullest possible understanding of the
numerous social and biological forces that interact to fuel the spread of
HIV in sub-Saharan Africa and beyond. At the individual level, MC provides
only partial protection against HIV infection. At the population level,
existing simulation models, with all of their limitations, suggest that
widespread MC is unlikely to provide complete control of HIV epidemics.
REFERENCES
1. Gray RH, Li X, Kigozi G, Serwadda D, Nalugoda F, Watya S, et al. The
impact of male circumcision on HIV incidence and cost per infection
prevented: a stochastic simulation model from Rakai, Uganda. Aids
2007;21(7):845-50.
2. Kahn JG, Marseille E, Auvert B. Cost-effectiveness of male circumcision
for HIV prevention in a South African setting. PLoS Med 2006;3(12):e517.
3. Nagelkerke NJ, Moses S, de Vlas SJ, Bailey RC. Modelling the public
health impact of male circumcision for HIV prevention in high prevalence
areas in Africa. BMC Infect Dis 2007;7:16.
4. Williams BG, Lloyd-Smith JO, Gouws E, Hankins C, Getz WM, Hargrove J,
et al. The potential impact of male circumcision on HIV in Sub-Saharan
Africa. PLoS Med 2006;3(7):e262.
5. Karim Q. Prevention of HIV by male circumcision. BMJ 2007;335:4-5.
On the potential impacts of male circumcision on Africa’s HIV epidemics from modelling and simulation
On the potential impacts of male circumcision on Africa’s HIV
epidemics from modelling and simulation
About male circumcision, the main question remains: What effects
could the scale-up of male circumcision [MC] have on the population-level
dynamics of the HIV epidemics in sub-Saharan Africa? Efforts to answer
this question have taken the form of mathematical modelling and simulation
exercises 1-4, inevitably involving considerable uncertainty.
Karim et al. 5 identified surgery as a key point of uncertainty.
Assuring the same quality than in trials, by using trained medical team
for surgery and counselling, with the same standard of care, particularly
the respect of healing period, are central points for implementing with
success circumcision program. Although we agree that the way to integrate
circumcision program in existing sexual health services may be “the
biggest challenge”, other points of uncertainty need to be raised once the
surgery is done.
The potential behavioral impacts of MC constitutes another
significant source of uncertainty. Now the susceptibility-reducing effect
of MC is quickly becoming common knowledge in many parts of sub-Saharan
Africa, men are likely to receive a very different message about the
protective effects of MC. Under these circumstances, circumcised men may
decrease their condom use or engage in riskier behaviour because they
perceive that MC provides full or partial protection against HIV. Another
reason to expect some impact of MC on sexual behavior involves changes in
the balance of power between women and men. MC could make it more
difficult for women to bargain for condom use with their male partners.
Circumcised men will be in a stronger position to argue that it is
unnecessary for them to use condoms since they have already taken dramatic
steps to reduce their risk of infection. The uncertainty here involves the
nature and magnitude of these behavioral impacts, and the population-level
consequences thereof. Gray and colleagues 1 found that a 25% increase in
the number of sexual partners could completely wipe out the population-
level effects of MC, and that a larger increase could cause HIV epidemics
to become substantially more severe than the baseline scenario.
Another consideration with respect to existing simulation models
involves uncertainty in estimates of current MC and HIV prevalence levels.
The prevalence of MC used in some simulation models is based upon data
that are several decades old and therefore must be considered with
caution. Moreover, using an average level of prevalence for a specific
country does not take account of the diversity that exists according to
ethnicities and geographical regions. Similarly, for many countries in sub
-Saharan Africa, historical and current estimates of HIV prevalence may be
inaccurate. This is especially true for countries that have relied upon a
small number of sentinel surveillance sites (e.g., antenatal clinics
attendees in urban areas) to obtain estimates of national HIV prevalence.
For many countries, estimates have improved in recent years as a result of
more systematic efforts to estimate national HIV prevalence levels, but
this progress has not been uniform. Clearly, inaccurate figures on current
levels of MC or HIV prevalence may lead to an incorrect baseline and
misleading conclusions for simulation studies.
Finally, leaving aside the simulation models, country level estimates
of current MC and HIV prevalence provide a sobering reminder that other
powerful forces besides MC are at work, such as social, cultural,
historical, religious or sexual factors. Consider for example Rwanda and
Zimbabwe in which it is estimated than 10% of men are circumcised 4. In
Rwanda, HIV prevalence is only 5% and in Zimbabwe it is 25% 4. These
figures strongly suggest that the association between MC prevalence and
the course of HIV epidemics is far from perfect. MC may be an important
tool for reducing the spread of HIV in some parts of sub-Saharan Africa.
But we must not allow our enthusiasm for this intervention to prevent us
from continuing to develop the fullest possible understanding of the
numerous social and biological forces that interact to fuel the spread of
HIV in sub-Saharan Africa and beyond. At the individual level, MC provides
only partial protection against HIV infection. At the population level,
existing simulation models, with all of their limitations, suggest that
widespread MC is unlikely to provide complete control of HIV epidemics.
REFERENCES
1. Gray RH, Li X, Kigozi G, Serwadda D, Nalugoda F, Watya S, et al. The
impact of male circumcision on HIV incidence and cost per infection
prevented: a stochastic simulation model from Rakai, Uganda. Aids
2007;21(7):845-50.
2. Kahn JG, Marseille E, Auvert B. Cost-effectiveness of male circumcision
for HIV prevention in a South African setting. PLoS Med 2006;3(12):e517.
3. Nagelkerke NJ, Moses S, de Vlas SJ, Bailey RC. Modelling the public
health impact of male circumcision for HIV prevention in high prevalence
areas in Africa. BMC Infect Dis 2007;7:16.
4. Williams BG, Lloyd-Smith JO, Gouws E, Hankins C, Getz WM, Hargrove J,
et al. The potential impact of male circumcision on HIV in Sub-Saharan
Africa. PLoS Med 2006;3(7):e262.
5. Karim Q. Prevention of HIV by male circumcision. BMJ 2007;335:4-5.
Competing interests:
None declared
Competing interests: No competing interests