A mass vaccination campaign in Chad in 2011 reduced all cases of meningitis by 94% and saw no cases of serogroup A meningococcal meningitis detected in 2012.
The finding comes from an evaluation by an international team including Oxford University scientists and led by the London School of Hygiene & Tropical Medicine and Centre de Support en Santé Internationale (CSSI) in Chad.
Several groups of bacteria can cause meningitis, the most important being meningococcus, which can trigger inflammation around the brain and spinal cord leading to disabilities such as deafness, paralysis, or death. The team looked at how a vaccine targeting serogroup A, the most common meningococci group in sub-Saharan Africa, affected both cases of infection and the number of people carrying the disease – carriers, who can transmit the infection through coughing and sneezing, can be detected by analysing throat swabs.
Approximately 1.8 million people aged 1-29 years received a single dose of PsA-TT (also known as MenAfriVac ®) in three regions of Chad in December 2011. The incidence of meningitis of any kind in these regions during the 2012 meningitis season was 2.5 per 100,000 people, compared to an incidence of 43.6 per 100,000 in regions where mass vaccination had not been undertaken – a 94% drop in the incidence of meningitis. No cases of serogroup A meningococcal meningitis were detected in the three vaccinated regions.
A report of the research is published in The Lancet.
Oxford University researchers, led by Professor Martin Maiden in the Department of Zoology, played a key role in the research by designing and leading the molecular characterisation of the bacterial specimens for the study. This involved developing and applying new genome-based approaches for identifying disease-associated and harmless meningococci present in throat swab samples.
'These approaches had to be rapid and precise yet inexpensive and were applied in Oxford to thousands of specimens collected in Chad,' said Professor Maiden. 'Our results demonstrate the effectiveness of the vaccine in halting a large epidemic in Chad and shows that the vaccine worked by preventing the transmission of the epidemic strain among healthy carriers. These findings will be valuable in designing vaccination programmes aimed at eliminating group A meningococcal disease from the "meningitis belt" of Africa.'
Professor Sir Brian Greenwood from the London School of Hygiene & Tropical Medicine, lead author of the study, said: 'This is one of the most dramatic outcomes from a public health intervention that I have seen during a long career of research in Africa. There are now real prospects that the devastating effects of this infection in Africa can be prevented.'
The new study was heavily influenced by carriage studies Professor Maiden and colleagues led in the UK in 1999-2001.
The study was funded by the Bill & Melinda Gates Foundation, the Wellcome Trust, and Médecins sans Frontières.