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BACKGROUND: Pneumococcal meningitis is a serious infection caused by Streptococcus pneumoniae. Published reports describe pneumococcal meningitis in patients with histories of previous head trauma. Currently licensed pneumococcal vaccines are not routinely recommended for persons with a history of head injury/brain surgery. We evaluated if the risk of hospitalization for pneumococcal meningitis was greater after hospitalization for head injury/brain surgery than after hospitalization for other reasons.
METHODS: Data are available for inpatient admissions to non-federal California licensed hospitals. ICD-9-CM diagnosis and procedure codes were used to identify exposed patients, defined as those with head injury/brain surgery during 1990–2012. The nonexposed group was a 1% random sample of all hospital discharges during 1990–2012, excluding hospital discharges for head injury/brain surgery, birth, or pregnancy-related conditions. Deaths were excluded from both groups. Records were matched to patients hospitalized with pneumococcal meningitis using a probabilistic matching algorithm based on social security number, demographic, and geographic characteristics to identify subsequent hospitalizations for pneumococcal meningitis among the exposed and unexposed groups. Risk ratios and 95% confidence intervals (CI) were calculated using logistic regression, controlling for whether or not the patient was in an age group recommended for pneumococcal vaccine at the time of their initial hospitalization.
RESULTS: There were 978,693 persons hospitalized for head injury/brain surgery; 73.4% were not in an age group recommended for pneumococcal vaccination during their initial hospitalization. One hundred fifty (0.015%) had a subsequent hospitalization for pneumococcal meningitis. A random sample of 816,860 patients without admissions for head injury/brain surgery were included, of whom 65 (0.008%) had a subsequent hospitalization for pneumococcal meningitis. Patients hospitalized for head injury/brain surgery were significantly more likely than patients hospitalized for other reasons to have a subsequent hospitalization for pneumococcal meningitis (RR=1.78, 95% CI=[1.54, 2.18]).
CONCLUSIONS: Head injuries and brain surgeries appear to nearly double the risk of subsequent pneumococcal meningitis. Limitations to this analysis include the probabilistic nature of the matching algorithm, missing pneumococcal meningitis hospitalizations that occurred after 2012, and the unknown pneumococcal vaccination status of hospitalized patients. It is possible that specific types of head injuries (e.g. concussions) do not increase the risk of subsequent pneumococcal meningitis, and inclusion of these patients could dilute the effect identified in this analysis. Additional analyses are needed to better define which groups may most benefit from vaccine, as well as further investigating the impact of the patient’s age and time at risk for pneumococcal meningitis.