Vaccine Effectiveness of Polysaccharide Vaccines Against Clinical Meningitis – Niamey, Niger, June 2015

Discussion Our simulated results suggest a fast increase of the VE after vaccination, reaching more than 80% after five days and 90% after ten days. Such high VE combined with the very high vaccine coverage measured in Niamey may have contributed to the rapidly decreasing incidence following the vaccination campaign. However, based on prior evaluations, polysaccharide vaccines provide a short duration of protection6,14,15 and do not impact nasopharyngeal carriage16, making them unsuitable for preventive vaccination campaigns. We observed a higher VE of the quadrivalent compared to the trivalent vaccine. This difference cannot be explained by the valences included in the vaccines as no NmY was isolated during the study period in Niamey. Further investigations, based on individual bacteriologic and vaccination data, are needed to understand these differences. This observational case control study presents a number of limitations. Only 14 (2.7%) of the clinical cases recruited in our evaluation were laboratory-confirmed. Due to this low number and the uncertainty in terms of representativeness of these cases regarding vaccination status, we decided not to compute VE against laboratory confirmed results. Lack of specificity in the suspected meningitis case definition used may have led to inclusion of cases due to other etiologies, leading to under-estimation of the VE. However, based on results in all age groups during the entire epidemic period, of the 1,456 specimens po...
Source: PLOS Currents Outbreaks - Category: Epidemiology Authors: Source Type: research