Background and purpose COVID‐19 continues to challenge neurologists in counseling persons with multiple sclerosis (pwMS) regarding disease‐modifying treatment (DMT) and vaccination. The objective here was to characterize predictors of COVID‐19 outcome in pwMS. Methods We included pwMS with polymerase chain reaction‐confirmed COVID‐19 diagnosis from a nationwide population‐based registry. COVID‐19 outcome was classified as either mild or severe. Impact of DMT, specifically anti‐CD20 monoclonal antibodies (anti‐CD20), and vaccination on COVID‐19 outcome was determined by multivariate models adjusted for a priori risk (determined by a cumulative risk score comprising age, disability, and comorbidities). Results Of 317 pwMS with COVID‐19 (mean age = 41.8 years [SD = 12.4], 72.9% female, median Expanded Disability Status Scale = 1.5 [range = 0–8.5], 77% on DMT [16% on anti‐CD20]), 92.7% had a mild course and 7.3% a severe course, with 2.2% dying from COVID‐19. Ninety‐seven pwMS (30.6%) were fully vaccinated. After a median 5 months from vaccination to SARS‐CoV‐2 infection (range = 1–9), severe COVID‐19 occurred in 2.1% of fully vaccinated pwMS compared to 9.5% in unvaccinated pwMS ( p = 0.018). A priori risk robustly predicted COVID‐19 severity ( R 2 = 0.605, p < 0.001). Adjusting for a priori risk, anti‐CD20 treatment was associated with increased COVID‐19 severity (odds ratio [OR] = 3.3, R 2 = 0.113, p = 0.003), but exposure to any other DMT was not. Fully vaccinated pwMS showed a significantly decreased risk for severe COVID‐19 (OR = 0.21, R 2 = 0.144, p < 0.001). Conclusions In a population‐based MS cohort, COVID‐19 course is primarily predicted by a priori risk (depending on age, disability, and comorbidities) explaining about 60% of variance. Anti‐CD20 treatment is associated with a moderately increased risk, whereas reassuringly vaccination provides protection from severe COVID‐19.

mentary oxygen with the Air-Viva lowered the inspired carbon dioxide concentration in a stepwise fashion, although the concentration did not reach zero even with 10 1 added oxygen/min. Comment Resuscitator bags refill with air during the patient's expiratory phase. To prevent rebreathing it is essential that the air intake and expired gases are separated. The valve of the Air-Viva, however, has a common port for both, which leads to expired gas being drawn into the bag during refilling. Supplementary oxygen, by displacement, reduces the amount of expired gas that enters the bag, so that the inspired carbon dioxide concentration falls as the flow of oxygen is increased. Nevertheless, as we found that the Air-Viva valve tended to obstruct when an oxygen flow of above 4 1/min was added it is impracticable to prevent rebreathing by using high flows of oxygen. The use of an International Standards Organisation model lung with added carbon dioxide is a standard method for demonstrating rebreathing in anaesthetic breathing systems, and the results obtained are comparable with clinical events.1 We were able to confirm these findings in two patients during the routine use of the Air-Viva bag. In both cases the inspired carbon dioxide concentration rose to 2% within 20 seconds. Resuscitation bags are used for the resuscitation and during the transport of critically ill patients. In both of these circumstances a raised inspired carbon dioxide concentration may have serious deleterious effects, such as raised intracranial pressure and peripheral vasodilatation. Rebreathing also, of course, implies a reduction in the inspired oxygen concentration. We believe, therefore, that the Air-Viva resuscitation bag should be withdrawn from use. Although it is no longer marketed (having been superceded by the Air-Viva 2), there are many such bags in general use. The Air-Viva 2 is of completely new design and performed satisfactorily in this test.

Background: The month-of-birth-effect (MoBE) describes the finding that multiple sclerosis (MS) patients seem to have been born significantly more frequently in spring, with a rise in May, and significantly less often in autumn and winter with the fewest births in November. Objectives: To analyse if the MoBE can also be found in the Austrian MS population, and if so, whether the pattern is similar to the reported pattern in Canada, United Kingdom, and some Scandinavian countries. Methods: The data of 7886 MS patients in Austria were compared to all live births in Austria from 1940 to 2010, that is, 7.256545 data entries of the Austrian birth registry and analysed in detail. Results: Patterns observed in our MS cohort were not different from patterns in the general population, even when stratifying for gender. However, the noticeable and partly significant ups and downs over the examined years did not follow the distinct specific pattern with highest birth rates in spring and lowest birth rates in autumn that has been described previously for countries above the 49th latitude. Conclusion: After correcting for month-of-birth patterns in the general Austrian population, there is no evidence for the previously described MoBE in Austrian MS patients.

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