AUTHOR=Matthes Katarina L. , Le Vu Mathilde , Bhattacharyya Urmila , Galliker Antonia , Kordi Maryam , Floris Joël , Staub Kaspar 

TITLE=Reinfections and Cross-Protection in the 1918/19 Influenza Pandemic: Revisiting a Survey Among Male and Female Factory Workers

JOURNAL=International Journal of Public Health

VOLUME=Volume 68 - 2023

YEAR=2023

URL=https://www.ssph-journal.org/journals/international-journal-of-public-health/articles/10.3389/ijph.2023.1605777

DOI=10.3389/ijph.2023.1605777

ISSN=1661-8564

ABSTRACT=Objectives: The COVID-19 pandemic highlights questions regarding reinfections and immunity resulting from vaccination and/or previous illness. Studies addressing related questions for historical pandemics are limited. Methods: We revisit an unnoticed archival source on the 1918/19 influenza pandemic. We analysed individual responses to a medical survey completed by an entire factory workforce in Western Switzerland in 1919. Results: Among the n=820 workers, 50.2% reported illness during the pandemic, the majority of whom reported severe illness. Among male workers 47.4% reported an illness vs. 58.5% of female workers, although this might be explained by varied age-distribution for each sex. Among those who reported illness, 15.3% reported reinfections. Reinfection rates increased across the three pandemic waves. The majority of subsequent infections were reported to be as severe as the first infection, if not more. Illness during the first wave, in summer 1918, was associated with a 35.9% (95%CI,15.7-51.1) protective effect against reinfections during later waves. Conclusion: Our study draws attention to a forgotten constant between pandemics: Reinfection and cross-protection have been a key topic, becoming increasingly important as the number of waves increases.