It's not just speculation on that level. Here is the conclusion from the linked paper verbatim: We identified at a population level that both older populations

It's not just speculation on that level. Here is the conclusion from the linked paper verbatim: We identified at a population level that both older populations and males are both more likely to die from COVID-19, and less likely to be seropositive for rubella-specific immunity, based on historical vaccination programmes of all three countries considered in this report. Finally, the hypothesis that this macro domain could be recognised by antibodies raised against rubella was supported by data that demonstrated that patients who have SARS-CoV2 infection had raised levels of rubella IgG to a level in keeping with secondary rubella infection. Taken together, we suggest that MMR will not prevent COVID-19 infection but could potentially reduce poor outcome. To conclude whether MMR vaccination can improve the outcomes from Covid-19 infection, a study using individual based data to compare MMR immunity status in the affected population is warranted. Source: https://www.medrxiv.org/content/10.1101/2020.04.10.20053207v1.full.pdf#page=7 https://www.medrxiv.org/content/10.1101/2020.04.10.20053207v...