Objective To determine if daily supplementation with cod liver oil, a low dose vitamin D supplement, in winter, prevents SARS-CoV-2 infection, serious covid-19, or other acute respiratory infections in adults in Norway. Design Quadruple blinded, randomised placebo controlled trial. Setting Norway, 10 November 2020 to 2 June 2021. Participants 34 601 adults (aged 18-75 years), not taking daily vitamin D supplements. Intervention 5 mL/day of cod liver oil (10 µg of vitamin D, n=17 278) or placebo (n=17 323) for up to six months. Main outcome measures Four co-primary endpoints were predefined: the first was a positive SARS-CoV-2 test result determined by reverse transcriptase-quantitative polymerase chain reaction and the second was serious covid-19, defined as self-reported dyspnoea, admission to hospital, or death. Other acute respiratory infections were indicated by the third and fourth co-primary endpoints: a negative SARS-CoV-2 test result and self-reported symptoms. Side effects related to the supplementation were self-reported. The fallback method was used to handle multiple comparisons. Results Supplementation with cod liver oil was not associated with a reduced risk of any of the co-primary endpoints. Participants took the supplement (cod liver oil or placebo) for a median of 164 days, and 227 (1.31%) participants in the cod liver oil group and 228 (1.32%) participants in the placebo group had a positive SARS-CoV-2 test result (relative risk 1.00, multiple comparison adjusted confidence interval 0.82 to 1.22). Serious covid-19 was identified in 121 (0.70%) participants in the cod liver oil group and in 101 (0.58%) participants in the placebo group (1.20, 0.87 to 1.65). 8546 (49.46%) and 8565 (49.44%) participants in the cod liver oil and placebo groups, respectively, had ≥1 negative SARS-CoV-2 test results (1.00, 0.97 to 1.04). 3964 (22.94%) and 3834 (22.13%) participants in the cod liver oil and placebo groups, respectively, reported ≥1 acute respiratory infections (1.04, 0.97 to 1.11). Only low grade side effects were reported in the cod liver oil and placebo groups. Conclusion Supplementation with cod liver oil in the winter did not reduce the incidence of SARS-CoV-2 infection, serious covid-19, or other acute respiratory infections compared with placebo. Trial registration ClinicalTrials.gov [NCT04609423][1]. Individual level data from the trial for the purposes outlined in the consent form can be shared with other researchers in a timely fashion. The data are regulated under the European GDPR regulative and sharing of data must be approved by the Data Protection Officer at Oslo University Hospital. The data dictionary, informed consent form, and analytic code will be made available at: at the time of publication. Data will be made available for researchers whose proposed use of the data has been approved. [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT04609423&atom=%2Fbmj%2F378%2Fbmj-2022-071245.atom

中文翻译：

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通过补充鱼肝油（一种低剂量维生素 D 补充剂）预防 covid-19 和其他急性呼吸道感染：四盲、随机安慰剂对照试验

目的 确定在冬季每天补充鱼肝油（一种低剂量的维生素 D 补充剂）是否可以预防挪威成年人的 SARS-CoV-2 感染、严重的 covid-19 或其他急性呼吸道感染。设计四盲、随机安慰剂对照试验。设置挪威，2020 年 11 月 10 日至 2021 年 6 月 2 日。参与者 34 601 名成年人（年龄 18-75 岁），未每日服用维生素 D 补充剂。干预 5 毫升/天的鱼肝油（10 微克维生素 D，n=17278）或安慰剂（n=17323）长达六个月。主要结果测量 预先定义了四个共同主要终点：第一个是由逆转录酶-定量聚合酶链反应确定的 SARS-CoV-2 检测结果呈阳性，第二个是严重的 covid-19，定义为自我报告的呼吸困难，入院住院，或者死亡。第三和第四个共同主要终点表明其他急性呼吸道感染：SARS-CoV-2检测结果呈阴性和自我报告的症状。与补充剂相关的副作用是自我报告的。后备方法用于处理多重比较。结果 补充鱼肝油与降低任何共同主要终点的风险无关。参与者服用补充剂（鱼肝油或安慰剂）的中位时间为 164 天，鱼肝油组的 227 名（1.31%）参与者和安慰剂组的 228 名（1.32%）参与者的 SARS-CoV-2 呈阳性测试结果（相对风险 1.00，多重比较调整置信区间 0.82 至 1.22）。在鱼肝油组的 121 名 (0.70%) 参与者和安慰剂组的 101 名 (0.58%) 参与者中发现了严重的 covid-19 (1. 20, 0.87 至 1.65)。鱼肝油组和安慰剂组分别有 8546 名 (49.46%) 和 8565 名 (49.44%) 参与者的 SARS-CoV-2 检测结果为 ≥1 次阴性 (1.00, 0.97 至 1.04)。鱼肝油组和安慰剂组分别有 3964 名（22.94%）和 3834 名（22.13%）参与者报告了≥1 次急性呼吸道感染（1.04，0.97 至 1.11）。鱼肝油和安慰剂组仅报告了低级副作用。结论与安慰剂相比，冬季补充鱼肝油并未降低 SARS-CoV-2 感染、严重 covid-19 或其他急性呼吸道感染的发生率。试验注册 ClinicalTrials.gov [NCT04609423][1]。出于知情同意书中所述目的，试验中的个人水平数据可以及时与其他研究人员共享。数据受欧洲 GDPR 监管，数据共享必须得到奥斯陆大学医院数据保护官的批准。数据字典、知情同意书和分析代码将在以下位置提供：在出版时。数据将提供给建议使用数据已获批准的研究人员。[1]：/lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT04609423&atom=%2Fbmj%2F378%2Fbmj-2022-071245.atom