Impact of Pneumococcal Conjugate Vaccines on Antibiotic-Nonsusceptible Invasive Pneumococcal Disease in the United States.

BACKGROUND Antibiotic-nonsusceptible invasive pneumococcal disease (NS-IPD) incidence declined dramatically in the United States following introduction of pneumococcal conjugate vaccines (PCVs) into the infant immunization schedule (7-valent PCV7 in 2000, replaced by the 13-valent PCV13 in 2010). We evaluated the long-term impact of PCVs on NS-IPD. METHODS We identified IPD cases through the Centers for Disease Control Active Bacterial Core surveillance during 1998-2018. Isolates intermediate or resistant to ≥1 antibiotic class were classified as nonsusceptible. We calculated annual rates of IPD (cases per 100,000 persons). RESULTS From 1998 through 2018, NS-IPD incidence decreased from 43.9 to 3.2 among children <5 years and from 19.8 to 9.4 among adults ≥65 years. Incidence of vaccine-type NS-IPD decreased in all age groups, while incidence of NVT NS-IPD increased in all age groups; the greatest absolute increase in NVT NS-IPD occurred among adults ≥65 years (2.3 to 7.2). During 2014-18, NVTs 35B, 33F, 22F, and 15A were the most common NS-IPD serotypes. CONCLUSIONS NS-IPD incidence decreased following PCV7 and PCV13 introduction in the United States. However, recent increases in NVT NS-IPD, most pronounced among older adults, have been observed. New higher valency PCVs containing the most common nonsusceptible serotypes, including 22F and 33F, could help further reduce NS-IPD.