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/10.1101/2020.04.10.20053207v...
No evidence of any difference in deadliness between age ranges in under 50s in UK excess deaths.
Other than that: Absolutely get an MMR vaccine if you don't have one. I wouldn't cound on it helping against Covid-19, but it helps against the Measles, which is a good enough reason to get it anyway.