#22: Trends in Bacterial Meningitis in a Tertiary-Level Children′s Hospital in Mexico, Following Haemophilus influenzae and Streptococcus pneumoniae Vaccination (1990–2018)
Authors: León-Lara X , Medina-Vera I , Arias de la Garza E , Macías-Parra M 
Published: March 2021

Abstract

Background
Bacterial meningitis (BM) remains a significant global health problem in pediatric care, with substantial morbidity and mortality. The epidemiology of BM has changed over the last 20 years. The ongoing introduction of conjugate vaccines for the most common meningeal pathogens has reduced the global incidence. However, there is limited epidemiologic and microbiologic data of BM in children before and after the widespread use of these vaccines in Mexico.

Methods
We conducted a retrospective, observational, analytical study. Pediatric patients (from 1 month to 18 years of age) presenting with BM and hospitalized at the Instituto Nacional de Pediatria in Mexico City, from 1990 to 2018, were included. Meningitis from invasive procedures or complicated head trauma were excluded. BM was classified according to the World Health Organization (WHO) criteria. The cases were analyzed in three periods: period A (1990–1999), period B (2000–2008), and period C (2009–2018). Period A corresponds to the time before the conjugate Haemophilus influenzae type b (Hib vaccine) was introduced in Mexico, while periods B and C correspond to the time after the Hib vaccine was routinely applied. Periods A and B correspond to the period before the pneumococcal conjugate vaccine (PCV7) was administrated in Mexico, while period C is after PCV7 and PCV13 were routinely administrated. The proportion of cases between periods was compared with Chi-square or Fisher exact test; P &lt; 0.05 was considered significant. Binomial logistic regression analysis was used to determine the association between potential risk factors and death due to BM.

Results
A total of 226 cases with BM were included, 180 (79.6%) confirmed cases, and 46 (20.4%) probable cases. The median age at diagnosis was 10 months. There were 126 (55.8%) cases in Period A, 62 (27.4%) cases in Period B, and 38 (16.8%) cases in Period C, with a statistically significant reduction between periods (P = 0.0001). Hib was the most commonly isolated pathogen, found in 38 (50%) cases. However, its proportion declined significantly after the introduction of the Hib conjugate vaccine (P &lt; 0.0001). S. pneumoniae followed as the second most commonly isolated bacterial pathogen. There was a significant reduction in neurological complications after the Hib conjugate vaccine (P = 0.003) and the S. pneumoniae conjugate vaccine (P = 0. 05) were introduced. Independent risk factors associated with mortality were coma (OR 15, P = 0. 0001), intracerebral bleeding (OR 3.5, P = 0.046), and pneumococcal meningitis (OR 9.4, P = 0. 002).

Conclusions
BM remains a cause of morbidity and mortality in pediatric patients in this hospital, with a dramatic change in the epidemiology since the introduction of the Hib conjugate vaccine to the national immunization schedule. Routine use of childhood conjugate vaccines against the most frequent etiological agents reduced the number of cases globally, mainly those caused by Hib. Additionally, conjugate vaccines reduced neurological complications and sequelae caused by this disease.