Serotype 3 associated invasive pneumococcal disease in children: analysis of 15 years of Australian national surveillance data

The 13-valent conjugate pneumococcal vaccine (13vPCV) replaced the 7vPCV in the Australian Immunisation Program in 2011 as a 3+0 schedule, updated to 2+1 schedule in 2018. We analysed national surveillance data to investigate the change in the incidence of pneumococcal serotype 3 (ST3) invasive pneumococcal disease (IPD) in preschool children. During 2009–2023 the incidence/100 000 children of ST3 IPD increased from 0.42 in 2009 to 3.65 in 2023. Compared with 2009–2011 (7vPCv), ST3 IPD incidence in 2012–2018 (13vPCV 3+0 dose) was almost four times higher and two times higher in 2019–2023 (13vPCV 2+1 dose) compared with 2012–2018 suggesting limited protection against ST3.