The purpose of this study is to learn how effective is PCV20 to help stop adults from getting pneumonia. Pneumonia is an infection of the lungs that can be caused by germs like bacteria, virus, or fungi. This study uses existing healthcare information. No participants will be actively enrolled. The information of participants will be taken from Kaiser Permanente Southern California's (KPSC) electronic health records (EHR). We will look at the EHR information for adults who meet the following points: * 18 years of age or older and a KPSC member as of 01 July 2022. * have been a KPSC member for at least one year before 01 July 2022. * have not received PCV15. * have had pneumonia or lower respiratory tract infection within 30 days of 01 July 2022. The study will begin from 01 July 2022 and will be followed through 30 June 2025. At the end of the follow-up period, the study will compare the number of pneumonia cases among people who receive PCV20 who do not receive it.