Invasive Pneumococcal Disease and Potential Impact of Pneumococcal Conjugate Vaccines Among Adults, Including Persons Experiencing Homelessness-Alaska, 2011-2020

Background. Adults aged >= 65 years, adults with certain underlying medical conditions, and persons experiencing homelessness are at increased risk for invasive pneumococcal disease (IPD). Two new pneumococcal conjugate vaccines, 15-valent pneumococcal conjugate vaccine (PCV15) and 20-valent pneumococcal conjugate vaccine (PCV20), were recently approved for use in U.S. adults. We described the epidemiology of IPD among Alaska adults and estimated the proportion of IPD cases potentially preventable by new vaccines.Methods. We used statewide, laboratory-based surveillance data to calculate and compare IPD incidence rates and 95% confidence intervals (CI) among Alaska adults aged >= 18 years during 2011-2020 and estimate the proportion of IPD cases that were caused by serotypes in PCV15 and PCV20.Results. During 2011-2020, 1,164 IPD cases were reported among Alaska adults for an average annual incidence of 21.3 cases per 100,000 adults per year (95% CI: 20.1-22.5). Incidence increased significantly during the study period (p<0.01). IPD incidence among Alaska Native adults was 4.7 times higher than among non-Alaska Native adults (95% CI: 4.2-5.2). Among adults experiencing homelessness in Anchorage, IPD incidence was 72 times higher than the general adult population (95% CI: 59-89). Overall, 1,032 (89%) Alaska adults with IPD had an indication for pneumococcal vaccine according to updated vaccination guidelines; 456 (39%) and 700 (60%) cases were caused by serotypes in PCV15 and PCV20, respectively.Conclusions. Use of PCV15 and PCV20 could substantially reduce IPD among adults in Alaska, including Alaska Native adults and adults experiencing homelessness.