Evaluation of Vaccine Safety After the First Public Sector Introduction of Typhoid Conjugate Vaccine-Navi Mumbai, India, 2018

Abstract

Background: In December 2017, the World Health Organization (WHO) prequalified the first typhoid conjugate vaccine (TCV; Typbar-TCV). While no safety concerns were identified in pre- and postlicensure studies, WHO's Global Advisory Committee on Vaccine Safety recommended robust safety evaluation with large-scale TCV introductions. During July-August 2018, the Navi Mumbai Municipal Corporation (NMMC) launched the world's first public sector TCV introduction. Per administrative reports, 113 420 children 9 months-14 years old received TCV.

Methods: We evaluated adverse events following immunization (AEFIs) using passive and active surveillance via (1) reports from the passive NMMC AEFI surveillance system, (2) telephone interviews with 5% of caregivers of vaccine recipients 48 hours and 7 days postvaccination, and (3) chart abstraction for adverse events of special interest (AESIs) among patients admitted to 5 hospitals using the Brighton Collaboration criteria followed by ascertainment of vaccination status.

Results: We identified 222/113 420 (0.2%) vaccine recipients with AEFIs through the NMMC AEFI surveillance system: 211 (0.19%) experienced minor AEFIs, 2 (0.002%) severe, and 9 serious (0.008%). At 48 hours postvaccination, 1852/5605 (33%) caregivers reported ≥1 AEFI, including injection site pain (n = 1452, 26%), swelling (n = 419, 7.5%), and fever (n = 416, 7.4%). Of the 4728 interviews completed at 7 days postvaccination, the most reported AEFIs included fever (n = 200, 4%), pain (n = 52, 1%), and headache (n = 42, 1%). Among 525 hospitalized children diagnosed with an AESI, 60 were vaccinated; no AESIs were causally associated with TCV.

Conclusions: No unexpected safety signals were identified with TCV introduction. This provides further reassurance for the large-scale use of Typbar-TCV among children 9 months-14 years old.

Keywords: adverse events following immunization; adverse events of special interest; typhoid conjugate vaccine; typhoid vaccination campaign.

Figure 1.

Most common safety-related events by assessment method among individuals who were reported to have received TCV¹—Navi Mumbai, India, 2018. ¹Typbar-TCV, Bharat Biotech International Limited, India. ²Per administrative reports. ³A total of 2023 children experienced at least 1 AEFI at either time point (48 hours or 7 days following TCV vaccination). At 7 days following vaccination, 172 of 343 children had reported an AEFI at 48 hours as well. ⁴Telephone interviews were conducted among 5605 caregivers of TCV recipients at 48 hours after vaccination. At 7 days following TCV vaccination, 4728 of those caregivers were interviewed again. ⁵Fever was the only AEFI reported among more than 1% of vaccine recipients 7 days following vaccination. Abbreviations: AEFI, adverse events following immunization; TCV, typhoid conjugate vaccine.