Despite introduction of PCVs, meningitis rates remain steady
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Although pneumococcal conjugate vaccines, or PCVs, have reduced infections caused by Streptococcus pneumonia, rates of meningitis have remained steady the emergence of pneumococcal strains not targeted by PCVs, according to a study published in The Pediatric Infectious Disease Journal.
“Bacterial meningitis is difficult to treat, has a high case fatality rate and generally leaves patients with long-term sequelae,” Reshmi Mukerji, MPH, of the department of microbiology at the University of Alabama at Birmingham, and David E. Briles, PhD, at the University of Alabama Birmingham, wrote. “The successful introduction of PCV7 followed by PCV13 in national immunization programs resulted in a sharp decrease in rates of invasive pneumococcal disease, both through protection against disease caused by serotypes present in the vaccines and through herd immunity against those serotypes. However, recent reports have consistently shown that the rates of pediatric and adult pneumococcal meningitis have either remained stable or increased, mainly due to the increase in carriage and subsequent meningitis caused by nonvaccine type (NVT) strains.”
Mukerji and Briles reviewed articles published from January 1930 to the present via PubMed, Google and Google Scholar using the terms S. pneumoniae, meningitis, serotype replacement, PCV, capsule type, capsule dependent disease and nasopharynx to brain transmission. They also used relevant references from identified articles and restricted their analysis to articles written in English.
Mukerji and Briles found that meningitis rates in children aged 1 to 59 months have been reported to be as high as 13 per 100,000 annually, caused mainly by NVT strains. Their research showed that PCVs have reduced rates of pneumococcal pneumonia by 35.4%, but meningitis cases by only 18.5% worldwide.
A Swedish study used in the analysis showed that, the introduction of the PCV7 and PCV13 vaccines, 38% and 18% of carriage isolates were non-PCV7 and non-PCV13 types, respectively. However, after the introduction of the vaccines, the percentage of non-PCV7 and non-PCV13 carriage isolates increased to 95% and 89%, respectively. Additionally, a U.S. study showed that, despite an overall decline in IPD cases including bacteremia, pneumonia and mastoiditis from 2009 to 2011, there was not much of a decline in meningitis cases.
Because of the prevalence of permanent neurologic sequelae and death in cases of pneumococcal meningitis, Mukerji and Briles said it would be beneficial to develop a vaccine capable of preventing meningitis regardless of capsular type.
“The high serotype diversity of these new replacement strains makes it problematic to expand the PCVs with enough capsular types to stem strain replacement and prevent the majority of pneumococcal meningitis,” Mukerji and Briles wrote. “One way to prevent pneumococcal meningitis is to completely eradicate pneumococcal colonization. This might be best done with a vaccine that targets the important pneumococcal virulence factors essential for colonization.” – by Eamon Dreisbach
Disclosures: The authors report no relevant financial disclosures.
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