Serotypes and antimicrobial resistance of in children under 5 years of age pre- and post-pneumococcal conjugate vaccine introduction in Paraguay.

remains a major cause of mortality and morbidity worldwide in children <5 years of age, even with advances in vaccination programmes. Reviewing and reporting trends in the distribution of pneumococcal serotypes and antimicrobial resistance in Paraguay will be useful for decision-making in public health.. This study analysed the serotype distribution and antimicrobial resistance of and the characteristics of pneumococcal disease in children <5 years old before and after the introduction of pneumococcal conjugate vaccines (PCVs). A total of 885 isolates and 278 PCR-positive clinical specimens were referred to the Central Laboratory of Public Health (LCSP) within the meningitis and pneumonia laboratory based-surveillance network in the period 2006-2020. Conventional and molecular microbiological techniques were used for confirmation and characterization. We identified 563 cases of pneumococcal disease in the pre-vaccination period, 325 cases in the post-PCV10 period and 275 cases in the post-PCV13 period. The serotypes covered by PCV10 decreased from 78.6-6.5 %. However, additional serotypes covered by PCV13 increased from 6.6-57.5% and non-PCV13 serotypes increased from 14.8-36.0 % (<0.001) in the post-PCV13 period. In cases of meningitis, the rate of resistance to penicillin decreased after the introduction of conjugate vaccines. No resistance to ceftriaxone was found in any period. In cases without meningitis, the rate of resistance to penicillin and ceftriaxone decreased slightly. However, the rate of resistance to erythromycin and tetracycline increased and that to trimethoprim-sulfamethoxazole (SXT) decreased in the post-PCV13 period compared to the pre-PCV period. The multidrug resistance rate was 8.5 %. A change in the circulating serotypes and antimicrobial resistance to certain antibiotics was observed. Non-vaccine serotype circulation and multidrug resistance may compromise the success of the conjugate vaccines.