Abstract
Background: Contemporary evidence on the incidence of typhoid fever is essential to inform decision making for typhoid prevention by vaccine introduction and non-vaccine measures. We aimed to update our previous systematic review and meta-analysis on the global incidence of typhoid fever.
Methods: We performed a systematic review of PubMed, Embase, Scopus, MEDLINE, Cochrane Central Register of Controlled Trials, Web of Science, and preprint repositories up to and including Dec 14 or 15, 2024, that encompassed primary, prospective, population-based, or hybrid surveillance reports of incidence data for culture-confirmed typhoid fever; this review was an update to our previous review that included studies published up to and including Jan 19, 2018. We performed an inverse variance, random-effects meta-analysis with log transformation of reports published from database inception up to and including Dec 14 or 15, 2024, and of new reports published from Jan 19, 2018, up to and including Dec 14 or 15, 2024, to generate pooled estimates of typhoid incidence per 100 000 person-years of observation (PYO). We conducted subgroup analyses by UN region, subregion, country, study quality, age group, and observation period, and performed meta-regression to explore sources of heterogeneity. This study was registered with PROSPERO (CRD42018086198).
Findings: We included 46 reports, yielding 107 estimates; of 21 673 records screened for this updated review, we included 14 reports, of which 13 were newer reports published since Jan 19, 2018, yielding 41 incidence estimates from 35 study sites in 15 countries. From new reports, the overall pooled incidence per 100 000 PYO was 206.3 (95% CI 63.6-669.6; I2=99.8%) from five population-based reports, and 132.5 (71.2-246.6; I2=99.9%) from eight hybrid surveillance reports. Incidence from new hybrid surveillance reports was highest in southern Asia at 320.6 (185.3-554.7) per 100 000 PYO (I2=99.9%). Incidence was higher in the 2 years to <5 years age group at 159.6 (60.3-422.1) per 100 000 PYO (I2=99.9%) compared with older age groups from new hybrid surveillance reports. Incidence from before 2010 was 127.4 (91.2-177.9) per 100 000 PYO (I2=97.4%) from population-based reports. Incidence from 2010 onwards was 118.8 (70.7-199.7) per 100 000 PYO (I2=99.9%) from hybrid surveillance reports. Meta-regression identified statistically significant moderators of effect size for population-based studies (p<0.0001) and hybrid surveillance studies (p=0.016). Egger's test for publication bias was statistically significant for population-based reports (p=0.0041) but not for hybrid surveillance reports (p=0.14). Of the 46 reports, we assessed six (13%) to be of high quality, 24 (52%) as moderate, and 16 (35%) as low quality.
Interpretation: Typhoid incidence was high in Africa and Asia, and among young children, thus affirming an ongoing need to prioritise vaccine and non-vaccine prevention of typhoid fever in this age group and for these UN regions.