Posted by: shigman | 05/08/2009

Disease Interactions

In a recent issue of The Lancet, Lowther et al. described a study looking at measles vaccination in a region with high HIV prevalence. Diseases, and interventions to control or treat diseases, often seem to be addressed individually. This stems from the lack of effective health systems and from the growth of vertical (disease-specific) programming.

 In reality, multiple disease agents co-exist and sometimes interact. 

For example, there may be: 

  • Co-infection with multiple agents
    • TB and HIV co-infection has received attention recently because of an increasing prevalence and mortality rate.
    • Multiple neglected tropical diseases occur in regions and co-infection makes treatment more complicated. 
  • Interaction between agents, as diseases affect one another
    • The link between sickle cell anemia and malaria has long been established.
    • HIV, which weakens the immune system, makes it easier for secondary infection to occur and harder for the body to deal with cancer.
    • Several bacterial or viral infections in children result in the development of pneumonia. 
  • Interaction between vaccines (or other preventive measures) and treatments
    • HIV-infected children are less likely to maintain immunity against measles following measles vaccination.
    • Combinations of drugs to fight multiple diseases may be toxic, resulting in debilitating side effects or a need for sequential rather than concurrent treatment.

 The design and implementation of research efforts to investigate the co-existence and co-occurrence of disease would be expensive. The studies would need to incorporate longitudinal and rigorous study designs to determine both short- and long-term health outcomes. They may need to focus on population-level as well as group-level sampling strategies. However, such studies would enable the medical and public health communities to better understand the disease impact and intervention needs, and hopefully to better meet the needs of people who are bombarded by concurrent diseases.

 Should large-scale studies be conducted on the impact of multiple diseases?

  • Is this a good use of resources – expensive?
  • What criteria should be used to select diseases to compare?

 Should infection status (antibody assay) be measured via vaccination campaigns?

  • Would it be cost effective?
  • What would be the logistical strategy?
  • Is more R&D to produce rapid assessment tools?

 What do you think?

 Paper:   Lowther SA, Curriero FC, Kalish BT, Shields TM, Monze M, Moss WJ. 2009. Population immunity to measles virus and the effect of HIV-1 infection after a mass measles vaccination campaign in Lusaka, Zambia: a cross-sectional survey.  The Lancet, Volume 373, Issue 9668, Pages 1025 – 1032.

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