An article published in The Lancet today has highlighted the possibility of establishing a World Serology Bank to better understand the dynamics of infectious disease dynamics, especially in an era where vaccinations against infectious diseases is becoming more and more prevalent. With rapid advance in diagnostic technologies, there has been impressive progress in what used to be tedious and time consuming tests. Now, using multiplex technology, a number of samples can be tested at one go, often for a number of pathogens, therefore, cutting the time requirement exponentially! However, it essentially remains a developed world solution for a problem that largely affects low and middle income countries. Image Credits: MedPage Today
The authors, in the summary of their article, state:
A central conundrum in the study of infectious disease dynamics is to define the landscape of population immunity. The proportion of individuals protected against a specific pathogen determines the timing and scale of outbreaks, and the pace of evolution for infections that can evade prevailing humoral immunity. Serological surveys provide the most direct measurement to define the immunity landscape for many infectious diseases, yet this methodology remains underexploited. To address this gap, we propose a World Serology Bank and associated major methodological developments in serological testing, study design, and quantitative analysis, which could drive a step change in our understanding and optimum control of infectious diseases.
- Group 1: Acute, immunizing, antigenically stable pathogens which confer lifetime protection and a positive serological response is a definite marker of past infection or vaccination. This group includes diseases like: measles, rubella and smallpox.
- Group 2: Immunizing, but antigenically variable pathogens, which may be raised in response to infection or immunization. This group includes diseases like dengue and avian influenza. The authors point out that the very reason there is a complexity in the immunology of these diseases (antigenic variability) is the reason which would provide a unique benefit if we had a better understanding of population level immunity – this would augment outbreak preparedness.
- Group 3: Infections which do not confer protective immunity, like TB, malaria and HIV. The authors identify the diseases in this group with a unique characteristic: though they do not confer immunity, they are a marker of previous or ongoing infection, and can thus lead us to a better understanding of the population level epidemiology of infectious diseases.
- Group 4: This group includes a number of infectious diseases, and they share the common characteristic that they “do not lead to reliably sustained, measurable antibody responses or for which presence of specific antibodies do not correlate with protection from future infection”.
The resource and manpower needed to have an effective serology bank, especially in the developing countries, could be immense. In fact, it could essentially be an impoverishing move in many countries with a high burden of infectious diseases. The fact that there needs to be regular re-testing of the samples raises questions regarding the storage, usage and handling of these samples.
These issues aside, in theory, this could provide us with a better snapshot of the infectious disease epidemiology at the moment and, in some cases, may even help us identify impending outbreaks, especially in cases of diseases which raise the titre of antibodies prior to onset of clinical signs. However, the system is essentially hobbled by the fact that the “test does not see what the tester does not look for”! In that, it would be a minimally successful endeavor in preventing outbreaks of novel infectious diseases. Keeping the global picture in mind, while it might seem attractive to invest in a World Serology Bank, it should be more effective, both from the point of costs and disease burden reduction, to invest in systems strengthening and capacity building in the developing world.
Metcalf, C., Farrar, J., Cutts, F., Basta, N., Graham, A., Lessler, J., Ferguson, N., Burke, D., & Grenfell, B. (2016). Use of serological surveys to generate key insights into the changing global landscape of infectious disease The Lancet DOI: 10.1016/S0140-6736(16)30164-7