Increased Age-Adjusted Cancer Mortality After the Third mRNA-Lipid Nanoparticle Vaccine Dose During the COVID-19 Pandemic in Japan







During the COVID-19 pandemic, excess deaths including cancer have become a concern in Japan, which has a rapidly aging population. Thus, this study aimed to evaluate how age-adjusted mortality rates (AMRs) for different types of cancer in Japan changed during the COVID-19 pandemic (2020-2022). Official statistics from Japan were used to compare observed annual and monthly AMRs with predicted rates based on pre-pandemic (2010-2019) figures using logistic regression analysis. No significant excess mortality was observed during the first year of the pandemic (2020). However, some excess cancer mortalities were observed in 2021 after mass vaccination with the first and second vaccine doses, and significant excess mortalities were observed for all cancers and some specific types of cancer (including ovarian cancer, leukemia, prostate cancer, lip/oral/pharyngeal cancer, pancreatic cancer, and breast cancer) after mass vaccination with the third dose in 2022. AMRs for the four cancers with the most deaths (lung, colorectal, stomach, and liver) showed a decreasing trend until the first year of the pandemic in 2020, but the rate of decrease slowed in 2021 and 2022. This study discusses possible explanations for these increases in age-adjusted cancer mortality rates.





Statistically significant increases in age-adjusted mortality rates of all cancer and some specific types of cancer, namely, ovarian cancer, leukemia, prostate, lip/oral/pharyngeal, pancreatic, and breast cancers, were observed in 2022 after two-thirds of the Japanese population had received the third or later dose of SARS-CoV-2 mRNA-LNP vaccine. These particularly marked increases in mortality rates of these ERα-sensitive cancers may be attributable to several mechanisms of the mRNA-LNP vaccination rather than COVID-19 infection itself or reduced cancer care due to the lockdown. The significance of this possibility warrants further studies. This article was previously posted to the Zenodo repository server on September 18, 2023.





Miki Gibo • Seiji Kojima • Akinori Fujisawa • Takayuki Kikuchi • Masanori Fukushima

Published: April 08, 2024    DOI: 10.7759/cureus.57860


Increased Age-Adjusted Cancer Mortality








Note: Prof. Masanori Fukushima is Professor Emeritus of the University of Kyoto, Director of the Translational Research Center for Medical Innovation, and the Foundation for Biomedical Research and Innovation, President of the Foundation of Learning Health Society Institute, former Director of the Outpatient Oncology unit of Kyoto University Hospital. He is the author of over 290 scientific publications.

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