Portuguese and British scientists develop mathematical model that explains variability in tuberculosis vaccine efficacy

HomeScience ReportsReports and NewsHealth and Medicine

Portuguese and British scientists develop mathematical model that explains variability in tuberculosis vaccine efficacy

04.03.2004

Scientists at the Instituto Gulbenkian de Ciencia (IGC), in Portugal, together with colleagues at the Universities of Lisbon and Warwick, in the United Kingdom, have developed a mathematical model that explains why the tuberculosis (TB) vaccine is ineffective in many of the developing countries. The model quantifies the predicted decrease in the number of TB cases in light of both the socioeconomic development of a population and the characteristics of new vaccines. Their research has been published in the Proceedings of the Royal Society (22nd March edition).

The efficacy of the bacille Calmette-Guérin (BCG) vaccine (the only vaccine in current use against tuberculosis) is variable, and there is no consensus about its usefulness. Estimates of protection range from 80% in the United Kingdom to around 0% in India, for example. For 30 years now scientists have tried to unravel the role of socioeconomic, genetic and environmental factors in generating this broad range of protection. This new model highlights socioeconomic factors (namely population density, access to primary healthcare, sanitation and diet, amongst others), which influence the dissemination of the infeccious agent.

The scientists estimate that the efficacy of the BCG vaccine decreases as the number of cases of TB increases, leading to a positive feedback loop, whose effect becomes most evident when the transmission potential reaches the reinfection threshold (a newly-defined concept). Other factors are expected to be involved, but no other model to date has been able to reproduce the magnitude of observed trends.

According to Gabriela Gomes, head of the Theoretical Epidemiology group at the IGC, the model shows that the vaccine is successful in blocking transmission in a population whose transmission potential is below the reinfection threshold (in these cases, most of the TB cases are due to primary infections). In those populations where the transmission potential exceeds the reinfection threshold, on the other hand, the protective effect of the vaccine is literally obliterated by the high levels of reinfection. The model predicts that, in these populations, only a vaccine with a stronger protective effect than a previous infection will successfully reduce transmission of tuberculosis.

In developed countries, the TB transmission potential is well below the reinfection threshold, due, largely, to major improvements in socioeconomic conditions, begun the mid-1800s. In less developed countries, on the other hand, the incidence of TB is up to 100 times higher. The poor socioeconomic conditions increase the potential for transmission, to levels clearly above the reinfection threshold. In these countries, changes in socioeconomic conditions are slow and difficult, therefore the scientists propose that the development of more potent vaccines is a more realistically hopeful measure for keeping TB under control. Their model also indicates the desired characteristics for such vaccines.

In Portugal the situation appears to one of delicate equilibrium, wherein any change may be sharply amplified. The number of reported cases of TB in Portugal points to transmission levels close to the reinfection threshold. The model predicts, therefore, that efforts to control tuberculosis will be greatly rewarded, but inattentiveness may result in a sharp rise in the number of cases.

The conclusions and predictions of this model are applicable to other diseases for which primary infection does not induce solid immunity. These diseases are kept prevalent by the high number of reinfections (malaria is an example of such a disease).

“This research underscores how important it is to combine mathematical modelling with experimental research in order to better understand infectious diseases, and developing effective therapeutical strategies”, says Antonio Coutinho, Director of the IGC.

Ana Coutinho | alfa
Further information:
http://www.igc.gulbenkian.pt

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Temperature-controlled fiber-optic light source with liquid core

In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.

Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...

Im Focus: Overdosing on Calcium

Nano crystals impact stem cell fate during bone formation

Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

All Focus news of the innovation-report >>>

Top

Send this article

Forum for Science, Industry and Business