Symptomatic MERS-CoV infection reduces the risk of future COVID-19 disease; a retrospective cohort study

BACKGROUND: The general human immune responses similarity against different coronaviruses may reflect some degree of cross-immunity, whereby exposure to one coronavirus may confer partial immunity to another. The aim was to determine whether previous MERS-CoV infection was associated with a lower risk of subsequent COVID-19 disease and its related outcomes. METHODS: We conducted a retrospective cohort study among all patients screened for MERS-CoV at a tertiary care hospital in Saudi Arabia between 2012 and early 2020. Both MERS-CoV positive and negative patients were followed up from early 2020 to September 2021 for developing COVID-19 infection confirmed by RT-PCR testing. RESULTS: A total of 397 participants followed for an average 15 months during COVID-19 pandemic (4.9 years from MERS-CoV infection). Of the 397 participants, 93 (23.4%) were positive for MERS-CoV at baseline; 61 (65.6%) of the positive cases were symptomatic. Out of 397, 48 (12.1%) participants developed COVID-19 by the end of the follow-up period. Cox regression analysis adjusted for age, gender, and major comorbidity showed a marginally significant lower risk of COVID-19 disease (hazard ratio = 0.533, p = 0.085) and hospital admission (hazard ratio = 0.411, p = 0.061) in patients with positive MERS-CoV. Additionally, the risk of COVID-19 disease was further reduced and became significant in patients with symptomatic MERS-CoV infection (hazard ratio = 0.324, p = 0.034) and hospital admission (hazard ratio = 0.317, p = 0.042). CONCLUSIONS: The current findings may indicate a partial cross-immunity, where patients with symptomatic MERS-CoV have a lower risk of future COVID-19 infection and related hospitalization. The present results may need further examination nationally using immunity markers.