key: cord-1035286-u3snc6a4 authors: Muscatello, David J; McIntyre, Peter B title: Comparing mortalities of the first wave of coronavirus disease 2019 (COVID-19) and of the 1918–19 winter pandemic influenza wave in the USA date: 2020-09-15 journal: Int J Epidemiol DOI: 10.1093/ije/dyaa186 sha: 12c110d0bced03562f665d0f932bcc4774362204 doc_id: 1035286 cord_uid: u3snc6a4 nan and 75 year age groups, respectively. The corresponding death rates per 100 000 population were 0.80, 24, 230, 740 and 2000, respectively, making crude, all-age mortality of 258 per 100 000 population almost uninterpretable for younger and older age groups. In New York City, the age-adjusted, all-age mortality rate for the 1918-19 winter wave of the influenza pandemic was 6.7 times higher than COVID-19 cumulative mortality rates to 2 June 2020. In <45-year-olds, the SMR was 42; that is, 42 times higher for influenza in 1918-19 than for COVID in 2020. In 45-year-olds, the SMR was 0.56; that is, 44% lower in 1918-19 than for COVID in 2020 (Table 1) . Applying these methods to more contemporary influenza data, the SMR for children (aged 17 years) for the 2009 H1N1 influenza pandemic in the USA is 2.1; that is, double the mortality for COVID-19 in New York City in the first 2020 wave. For older age groups, the SMR is less than 0.05, or more than 20-fold lower ( Table 2 ). In New York City, all-age COVID-19 mortality rates remain substantially lower than those documented in the 1918-19 influenza pandemic, recognizing that 1918-19 mortality was inflated by lack of now routine treatments, such as antibiotics, supplemental oxygen and ventilatory support. In children, recent severe seasonal influenza mortality was similar to, and 2009 pandemic mortality double, that documented in the first 3 months of the COVID-19 epidemic. In older people, COVID-19 mortality is more than 10-fold higher than a severe influenza season, and more than 300-fold higher than the 2009-10 influenza pandemic. Limitations of this study include that deaths from COVID-19 in New York City continue to be reported, so SMRs may change, and ascertainment of COVID-19 deaths may have been reduced by insensitivity of earlier COVID-19 diagnostics, 9 with evidence of underascertainment of COVID-19-attributable deaths by routine surveillance. 10 It is also unknown whether changes in exposure and consequent immunity over time and by place will have an impact on the age-specific risk of severe illness, if infection by this new human coronavirus is sustained in human populations. Observed differences in clinical severity and mortality risk by age among emerging pandemic strains or coronaviruses or influenza viruses may reflect herd immunity conferred on different age cohorts by exposure to previously circulating strains of the same virus. 11 In New York City in 1918-19, measures invoked included isolation of infected individuals, enhanced disease surveillance, and education campaigns but, unlike in 2020, not school closures. 12, 13 Comparisons with 1918-19 must also take into account the prominent role of secondary bacterial infection in influenza mortality and the lack of now routine treatments. However, it seems unlikely that these factors could fully explain a 40-fold lower mortality below 45 years of age for COVID-19 in New York City. Notwithstanding the substantial burden of less severe infections due to both influenza and COVID-19 in different age groups, and the possibility that risk of death may vary over time, the higher age-specific mortality in the young in both the 1918-19 and 2009 influenza pandemics compared with COVID-19 is an important factor for decisions about whole-of-population versus age-targeted vaccination strategies. No specific funding was received for this project. 2020 COVID-19 confirmed and probable death rates by age (as at 2 June 2020). 5 Of 21 649 deaths, 1 (0.0046%) death with unknown age and 198 (0.91%) with incomplete age information were excluded. Extraordinary diseases require extraordinary solutions Pandemic versus epidemic influenza mortality: a pattern of changing age distribution United States Census Bureau. A Century of Population Change in the Age and Sex Composition of the Nation Comparisons between countries are essential for the control of COVID-19 COVID-19: Data Epidemiological evidence of an early wave of the 1918 influenza pandemic in New York City Estimating the burden of 2009 pandemic influenza A (H1N1) in the United States Estimated Influenza Illnesses, Medical Visits, Hospitalizations, and Deaths and Estimated Influenza Illnesses, Medical Visits, Hospitalizations, and Deaths Averted by Vaccination in the United States Interpreting diagnostic tests for SARS-CoV-2 DOHMH) COVID-19 Response Team. Preliminary estimate of excess mortality during the COVID-19 outbreak Immunopathogenesis of COVID-19 and early immunomodulators The 1918 influenza epidemic in New York City: a review of the public health response COVID-19: Prevention and Groups at Higher Risk The authors would like to acknowledge Donald R Olson for helpful advice on the manuscript. None declared.