Evaluation of Pertussis Disease in Young Infants in India: A Hospital-Based Multicentric Observational Study.

Objectives: To evaluate the incidence of laboratory-confirmed pertussis (LCP) among infants hospitalized with acute respiratory infections (ARIs) and meeting the Centers for Disease Control and Prevention (CDC)-recommended clinical case definition. Methods: An investigator-initiated active surveillance for clinically suspected cases (CSCs) of pertussis screened infants aged ≤6 mo hospitalized with ARIs during January 2020-April 2022 at seven centers across India. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect Bordetella pertussis in nasopharyngeal swabs. Infants were classified as having 'LCP' or 'probable pertussis' (PP). Results: Among 1102 screened infants, 400 participants met the CDC-2020 clinical case definition for pertussis. Of these, 34/400 (8.5%) had LCP and 46/400 (11.5%) had PP. The proportion of participants with LCP and PP was similar among infants aged 0-3 and 4-6 mo [LCP: 0-3 mo, 21/248 (~9%); 4-6 mo, 13/152 (~9%); PP: 0-3 mo, 30/248 (~12%); 4-6 mo, 16/152 (~11%)]. Cough illness lasted ≥2 wk in 3/34 (~9%) and 34/46 (~74%) participants with LCP and PP, respectively. Notably, 80% CSCs had neither LCP nor PP, and a respiratory pathogen apart from B. pertussis was detected in ~32%. Ventilation was required in 12 participants with LCP/PP. Conclusions: In this first study from India based on revised CDC guidelines, the incidence of LCP was 8.5%; cough illness was not a predominant feature. Infants below the age appropriate for vaccination are prone to pertussis-related hospital admissions, ICU care, and ventilation. Maternal immunization may be evaluated for neonatal protection, in addition to other strategies, to decrease disease burden in this highly vulnerable group. Clinical Trial Registration Number: CTRI/2019/12/022449. [ABSTRACT FROM AUTHOR]