Background The WHO recommends vaccines for prevention and control of typhoid fever, especially where antimicrobial-resistant typhoid circulates. In 2018 the Navi Mumbai Municipal Corporation (NMMC), implemented a TCV campaign. The campaign targeted all children aged 9-months through 14-years within NMMC boundaries (∼320,000 children) over 2 vaccination phases. The phase 1 campaign occurred from July 14-August 25, 2018 (71% coverage, ∼113,420 children). We evaluated the phase 1 campaign’s programmatic effectiveness in reducing typhoid cases at the community level. Methods We established prospective, blood culture-based surveillance at 6 hospitals in Navi Mumbai, offering blood cultures to children presenting with fever ≥ 3 days. We employed a cluster-randomized (by administrative boundary) test-negative design to estimate the effectiveness of the vaccination campaign on pediatric typhoid cases. We matched test-positive, culture-confirmed typhoid cases with up to 3 test-negative, culture-negative controls by age and date of blood culture and assessed community vaccine campaign phase as an exposure using conditional logistic regression. Results Between September 1, 2018–March 31, 2021, we identified 81 typhoid cases and matched these with 238 controls. Cases were 0.44 times as likely to live in vaccine campaign communities (programmatic effectiveness, 56%, 95%CI: 25%-74%, p=0.002). Cases ≥ 5-years-old were 0.37 times as likely (95% CI: 0.19-0.70; p-value = 0.002) and cases during the first year of surveillance were 0.30 times as likely (95% CI: 0.14-0.64; p-value = 0.002) to live in vaccine campaign communities. Conclusions Our findings support the use of TCV mass vaccination campaigns as effective population-based tools to combat typhoid fever.

Background:The WHO recommends vaccines for prevention and control of typhoid fever, especially where antimicrobial-resistant typhoid circulates. In 2018 the Navi Mumbai Municipal Corporation (NMMC), implemented a TCV campaign. The campaign targeted all children aged 9-months through 14-years within NMMC boundaries (~320,000 children) over 2 vaccination phases. The phase 1 campaign occurred from July 14-August 25, 2018 (71% coverage, ~113,420 children). We evaluated the campaign's programmatic effectiveness in reducing typhoid cases at the community level.Methods:We established prospective, blood culture-based surveillance at 6 hospitals in Navi Mumbai, offering blood cultures to children presenting with fever for at least 3 days. We employed a cluster-randomized test-negative design to estimate the effectiveness of the vaccination campaign on pediatric typhoid cases. We matched culture-confirmed typhoid cases with up to 3 culture-negative controls by age and date of blood culture and assessed community vaccine campaign phase as an exposure using conditional logistic regression.Results:Between September 1, 2018-March 31, 2021, we identified 81 typhoid cases and matched these with 238 controls. Cases were 0.44 times as likely to live in vaccine campaign communities (campaign effectiveness, 56%, 95%CI: 25%-74%, p=0.002). Cases ≥ 5-years-old were 0.37 times as likely (95% CI: 0.19-0.70; p-value = 0.002) and cases during the first year of surveillance were 0.30 times as likely (95% CI: 0.14-0.64; p-value = 0.002) to live in vaccine campaign communities.Conclusions:Our findings support the use of TCV mass vaccination campaigns as effective population-based tools to combat typhoid fever.

We performed whole genome sequencing of 174 Salmonella Typhi and 54 Salmonella Paratyphi A isolates collected through prospective and retrospective surveillance in the context of a phased typhoid conjugate vaccine introduction in Navi Mumbai, India. We investigate the temporal and geographical patters of emergence and spread of antimicrobial resistance. Additionally, we evaluated the relationship between the spatial distance between households and genetic clustering of isolates using hierarchical Bayesian models. Most isolates were non-susceptible to fluoroquinolones, with nearly 20% containing ≥3 mutations in the quinolone resistance determining region, conferring high-level resistance. Two H58 isolates carried an IncX3 resistance plasmid containing blaSHV-12, associated with ceftriaxone resistance, suggesting that the ceftriaxone-resistant S. Typhi isolates from India have evolved independently on multiple occasions. Among S. Typhi isolates, we identified two main clades circulating in Navi Mumbai (2.2 and 4.3.1 [H58]); 2.2 isolates were closely related following a single introduction around 2007, whereas H58 isolates had been introduced multiple times to the city. Increasing geographic distance between isolates was strongly associated with genetic clustering (OR 0.72 per km; 95% CrI: 0.66-0.79). This effect was seen for distances up to 5 km (OR 0.65 per km; 95% CrI: 0.59-0.73) but was not seen for distances beyond 5 km (OR 1.02 per km; 95% CrI: 0.83-1.26). Our findings indicate that S. Typhi was repeatedly introduced into Navi Mumbai and then spread locally, with strong evidence of spatial-genetic clustering. In addition to vaccination, local interventions to improve water and sanitation will be critical to interrupt transmission.

India has one of the highest estimated burdens of enteric fever globally. Prior to implementation of Typbar-TCV typhoid conjugate vaccine (TCV) in a public sector pediatric immunization campaign in Navi Mumbai, India, we conducted a retrospective review of blood culture-confirmed cases of typhoid and paratyphoid fevers to estimate the local burden of disease. This review included all blood cultures processed at a central microbiology laboratory, serving multiple hospitals, in Navi Mumbai (January 2014 to May 2018) that tested positive for either Salmonella Typhi or Salmonella Paratyphi A. Of 40,670 blood cultures analyzed, 1,309 (3.2%) were positive for S. Typhi (1,201 [92%]) or S. Paratyphi A (108 [8%]). Culture positivity was highest in the last months of the dry season (April-June). Our findings indicate a substantial burden of enteric fever in Navi Mumbai and support the importance of TCV immunization campaigns and improved water, sanitation, and hygiene.

India has one of the highest estimated burdens of enteric fever globally. Prior to the implementation of Typbar-TCV typhoid conjugate vaccine (TCV) in a public sector pediatric immunization campaign in Navi Mumbai, India, we conducted a retrospective review of blood culture-confirmed cases of typhoid and paratyphoid fevers to estimate the local burden of disease. This review included all blood cultures processed at a central microbiology laboratory, serving multiple hospitals, in Navi Mumbai (January 2014–May 2018) that tested positive for either Salmonella Typhi or Salmonella Paratyphi A. Of 40,670 blood cultures analyzed, 1,309 (3.2%) were positive for S. Typhi (1,201 [92%]) or S. Paratyphi A (108 [8%]). Culture positivity was highest in the last months of the dry season (April–June). Our findings indicate a substantial burden of enteric fever in Navi Mumbai and support the importance of TCV immunization campaigns and improved water, sanitation, and hygiene.