January 14, 2016
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Pediatric vaccines substantially reduce bacterial meningitis in adults

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The incidence of adult bacterial meningitis has decreased substantially in the Netherlands, partly due to herd protection offered by pediatric conjugate vaccines, according to a study published in The Lancet Infectious Diseases.

Researchers from the University of Amsterdam prospectively assessed patients aged 16 years and older who had community-acquired bacterial meningitis from 2006 through June 2014. The researchers focused on causative pathogens, clinical characteristics and outcomes of the disease after the introduction of adjunctive dexamethasone treatment and the national implementation of pediatric conjugate vaccines.

In all, they assessed 1,412 episodes of community-acquired bacterial meningitis.

According to the researchers, disease incidence declined from 1.72 cases per 100,000 adults annually during 2007-2008 to 0.94 cases per 100,000 adults annually for 2013-2014. Streptococcus pneumoniae had caused 72% of episodes.

Rates of adult bacterial meningitis decreased most sharply among pneumococcal serotypes included in the pediatric conjugate vaccine, and in meningococcal meningitis. The researchers observed no evidence of serotype or serogroup replacement.

Of all episodes, 17% were fatal, while an unfavorable outcome occurred in 38%. Predictors of unfavorable outcomes were advanced age, absence of otitis or sinusitis, alcoholism, tachycardia, low score on the Glasgow Coma Scale, cranial nerve palsy, a cerebrospinal fluid white-cell count less than 1,000 cells/μL, a positive blood culture and a high serum C-reactive protein concentration. Among assessed episodes (n = 1,384), 89% saw the administration of adjunctive dexamethasone. The adjusted OR of dexamethasone treatment for unfavorable outcomes was 0.54 (95% CI, 0.39-0.73).

“Our findings show the substantial improvement in the prognosis of pneumococcal meningitis over the past 2 decades and the effect of pediatric conjugate vaccines on adult bacterial meningitis,” the researchers wrote. “Herd protection is a major part of the effectiveness of conjugate vaccines and can protect those with poor immunological response to vaccination — eg, infants and elderly people. The development of vaccines covering more pneumococcal serotypes, new potent anti-inflammatory treatments, starting treatment immediately after blood cultures are obtained, and aggressive supportive care might further improve the prognosis of patients with bacterial meningitis.”

In a related editorial, Pere Domingo, MD, and Virginia Pomar, MD, PhD, from the infectious diseases unit at Hospital de la Santa Creu i Sant Pau, Universitat Autònoma de Barcelona, Spain, noted that these findings are consistent with results of other epidemiological- and hospital-based studies.

“Immunization is one of the most successful and cost-effective health interventions known, and the only one that has led to the eradication of an infectious disease,” they wrote. “Therefore, vaccines against meningeal pathogens should lower the burden of the disease. Most of the future progress in bacterial meningitis will come from preventive rather than therapeutic measures, especially if effective, universal, and broad-coverage vaccines can be made available and affordable wherever they are most needed.” – by Jason Laday

Disclosure: The researchers report no relevant financial disclosures.