As of 2022, the bottom 50 percent in Chile, that is, the population whose income lied below the median, earned on average 4,800 U.S. dollars at purchasing power parity (PPP) before income taxes. This is nearly 43 times less than the average income of the top ten percent, that stood at 215,000 USD that year. In relation to percentage distribution of national wealth in Chile, the top ten percent accounted for over 80 percent of the overall national wealth.

Objective: To investigate the frequency of coronavirus disease (COVID-19) in patients with multiple sclerosis (pwMSs) living in a high socioeconomic vulnerability area in Chile.

Methods: In this prospective cohort study, we compared the frequency of COVID-19 in 52 Chilean pwMSs on disease-modifying treatments (DMTs), living in urban municipalities with low-income/high-poverty levels, with that previously reported in pwMSs living in municipalities with high-income/low-poverty rates in Santiago, Chile. Demographic and clinical features of the pwMSs were obtained from their last consultation between March 3, 2020, and August 29, 2020.

Results: In the low-income pwMSs, the mean patient age was 34 years, 69% were women, mean disease duration was 3 years, and mean Expanded Disability Status Scale score was 1.6. Of these, 61.5% pwMSs (32/52) underwent quarantine during the study period. COVID-19 diagnosis was confirmed by reverse transcriptase polymerase chain reaction in five patients (10%): two were on glatiramer acetate, one was on fingolimod, and two were on alemtuzumab. All pwMSs with COVID-19 recovered fully. The previously reported frequency of confirmed COVID-19 in middle‒upper income pwMSs living in Santiago was 1%. The frequency of COVID-19 among pwMSs in the low- and middle‒high income inhabitants of Santiago differed significantly (z = -4.3235, p < 0.00001; one-tailed Fisher exact test, p < 0.01).

Conclusion: The frequency of COVID-19 in the low-income/high-poverty cohort in Santiago, Chile, was markedly high. Accordingly, high socioeconomic vulnerability should be considered as an important risk factor for COVID-19 in pwMSs.