BACKGROUND The COVID-19 pandemic could impact frequency and mortality of non-COVID-19 community-acquired pneumonia (CAP). Changes in frequency, patient mix, treatment, and organ dysfunction could cascade together to increase mortality of CAP during compared to pre-COVID-19. METHODS: Hospitalized CAP patients at St. Paul's Hospital, Vancouver, Canada pre- (fiscal years 2018/2019 and 2019/2020) and during COVID-19 pandemic (2020/2021 and 2021/2022) were evaluated. RESULTS: In 5219 CAP patients, there was no significant difference pre- versus during pandemic in mean age, gender and Charlson co-morbidity score. However, hospital mortality increased significantly from pre- versus during COVID-19 (7.5% versus 12.1% respectively, [95% CI for difference: 3.0-6.3%], p<0.001), a 61% relative increase, coincident with increases in ICU admission (18.3% versus 25.5% respectively, [95% CI for difference: 5.0-9.5%] p<0.001, 39% relative increase) and ventilation (12.7% versus 17.5%, respectively, [95% CI for difference: 2.8-6.7%] p<0.001, 38% relative increase). Results remained the same after regression adjustment for confounders. CAP hospital admissions decreased 27% from pre- (n=1349 and 1433, 2018/2019 and 2019/2020 respectively) versus the first COVID-19 pandemic year (n=1047 in 2020/2021) then rose to pre-pandemic number (n=1390 in 2021/2022). During pre-pandemic years, CAP admissions peaked in winter; during COVID-19, the CAP admissions peaked every six months. CONCLUSIONS AND RELEVANCE: The COVID-19 pandemic was associated with increases in hospital mortality, ICU admission and invasive mechanical ventilation rates of non-COVID-19 CAP and a transient, one year frequency decrease. There was no winter seasonality of CAP during the COVID-19 pandemic era. Future pandemic planning for CAP hospital care is needed.

Drs. Lee, Boyd and Kalil declare that they have no conflict of interest. Dr Walley has received Foundation Grant from the Canadian Institutes for Health Research, held by UBC. He is the Chair of a DSMB for Northern Therapeutics, unpaid service. Dr Cawcutt received payment from Becton, Dickinson and Company for advisory meeting participation and speaking related to sepsis from October 2022. Dr. Russell reports patents owned by the University of British Columbia (UBC) that are related to (1) the use of PCSK9 inhibitor(s) in sepsis, (2) the use of vasopressin in septic shock and (3) a patent owned by Ferring for use of selepressin in septic shock. Dr. Russell is an inventor on these patents. Dr. Russell was a founder, Director and shareholder in Cyon Therapeutics Inc. (now closed) and is a shareholder in Molecular You Corp. Dr. Russell is Senior Research Advisor of the British Columbia, Canada Post COVID Interdisciplinary Clinical Care Network (PC-ICCN). Dr. Russell is no longer actively consulting for any industry. Dr. Russell reports receiving consulting fees in the last 3 years from: 1. Dr. Russell was a funded member of the Data and Safety Monitoring Board (DSMB) of an NIH-sponsored trial of plasma in COVID-19 (PASS-IT-ON) (2020-2021). 2. PAR Pharma (sells prepared bags of vasopressin). Dr. Russell has received grants for COVID-19 and for pneumonia research: 4 from the Canadian Institutes of Health Research (CIHR) and 3 from the St. Paul's Foundation (SPF). Dr. Russell was a non-funded Science Advisor and member, Government of Canada COVID-19 Therapeutics Task Force (June 2020-2021).

The co-authors were supported by Canadian Institutes of Health Research, Grant number: 473647 to Dr. James A. Russell. St. Paul's Hospital Foundation grant to Dr. James A. Russell. Dr. John Boyd is a recipient of a Providence Health Care Research Scholarship. Dr. Keith Walley is supported by Canadian Institutes of Health Research (CIHR) Foundation Grant FDN 154311. Dr. James A. Russell is the Senior Research Advisor of the British Columbia, Canada Post-COVID Condition - Interdisciplinary Clinical Care Network (PC-ICCN).

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

This study was approved by the Providence Health Care and University of British Columbia (UBC) Human Research Committee as low risk and no consent was required.

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes

All data produced in the present work are contained in the manuscript