2903. Post PCV13 Dynamics of NonVaccine Serotype (NVT): Disproportionate Increase of the Additional PCV20 Candidate Serotypes in Respiratory and Invasive Disease in Young Children

BACKGROUND: PCV13 implementation in children resulted in a substantial decline in carriage of and disease by vaccine serotypes (VT13). However, disease caused by non-PCV13 serotypes (NVT) is still relatively prevalent and even increasing, leading to an effort to develop a 20-valent vaccine (PCV20), containing the additional 7 serotypes: 8, 10A, 11A, 12F, 15B/C, 22F, 33F (VT20-13). We assessed dynamics of VT13, VT20-13, and non-PCV20 (NVT20) in nasopharyngeal carriage, respiratory infections, and IPD in children < 2 years following PCV13 implementation. METHODS: Multiple prospective, population-based surveillance projects, conducted in Israel between 2009 and 2017 were used. We studied isolates from IPD; otitis media (OM); conjunctivitis; carriage in healthy children; carriage during lower respiratory tract infections with chest radiography examination (LRI); and carriage during non-LRI illnesses. We added data from healthy children in the community since 2011. Prevalence rate ratios were calculated, comparing VT13, VT20-13 and NVT20 rates in late-PCV13 (2015–2017) vs. early-PCV (2009–2011) periods. RESULTS: Overall, 9,089 episodes were recorded. VT13 declined significantly in all 6 groups by 75–86% (Figures 1 and 2). Proportions of VT20-13 significantly increased in all groups, excluding conjunctivitis. The highest increases were observed in IPD, OM, and carriage during LRI. In 2015–2017, VT20-13 consisted 24%, 23%, and 19% of carriage in healthy children, carriage in non-LRI illness, and conjunctivitis, respectively, vs. 51%, 33%, and 32% in IPD, OM, and carriage during LRI. VT20-13 rapidly became the leading fraction in IPD. NVT20 proportions increased in all groups. CONCLUSION: (1) PCV13 implementation resulted in a substantial increase in NVT carriage and disease; (2) In IPD, VT20-13 became the dominant group; (3) The increases in the proportion of VT20-13 seen in OM and carriage during LRI was significantly higher than in conjunctivitis and in carriage without LRI. [Image: see text] [Image: see text] DISCLOSURES: All Authors: No reported Disclosures.