CDC updates guidance on COVID-19, studies show vitamins don't improve outcomes

The CDC offered new guidance on immunocompromised patients and pulse oximetry's accuracy, and recent trials showed that vitamin D, zinc, and ascorbic acid didn't help COVID-19 patients but prophylactic anticoagulation did.


The CDC made multiple small updates to its guidance on COVID-19. On Feb. 18, it alerted clinicians that some severely immunocompromised persons with COVID-19 may remain infectious beyond 20 days after their symptoms began and require additional testing and expert consultation before they leave isolation. On Feb. 12, the agency encouraged clinicians to be aware that pulse oximeters may exhibit suboptimal accuracy in certain populations. The guidance cites a study that found occult hypoxemia went undetected by pulse oximetry nearly three times more frequently in hospitalized Black patients than White patients. The FDA issued a safety communication on the same topic on Feb. 19, urging clinicians to be aware of the many factors that can affect accuracy (including poor circulation, skin pigmentation, skin thickness, skin temperature, current tobacco use, and use of fingernail polish) and make decisions based on trends rather than absolute thresholds.

Vitamin D3 did not improve outcomes in hospitalized patients with COVID-19, according to a study published by JAMA on Feb. 17. It included 240 Brazilian patients, half of whom were randomized to a single oral dose of 200,000 IU of vitamin D3 and half who were randomized to placebo. There were no significant differences between groups in median length of stay, in-hospital mortality, ICU admission, or need for mechanical ventilation. Mean serum levels of 25-hydroxyvitamin D were higher in the active treatment group (44.4 ng/mL vs. 19.8 ng/mL), suggesting that higher levels do not help. “The findings do not support the use of a high dose of vitamin D3 for treatment of moderate to severe COVID-19,” the authors concluded, although they cautioned that the results cannot necessarily be extrapolated to other geographic regions, which could have more vitamin D deficiencies.

Zinc and ascorbic acid don't help either, according to a trial of outpatients with COVID-19 published by JAMA Network Open on Feb. 12. It randomized 214 U.S. patients with positive tests and symptoms in a 1:1:1:1 ratio to 10 days of zinc gluconate (50 mg), ascorbic acid (8,000 mg), both, or neither. The study was stopped early for futility. There was no significant difference among the four groups on the primary end point, the number of days required to reach a 50% reduction in symptoms. The authors concluded that these supplements should not be recommended for patients with COVID-19. “Most consumers of ascorbic acid and zinc are taking significantly lower doses of these supplements, so demonstrating that even high-dose ascorbic acid and zinc had no benefit suggests clear lack of efficacy. In addition, administering supplements with unproven benefit can be detrimental due to adverse effects,” they wrote.

Lack of evidence or recommendations did not prevent outpatient use of drugs and supplements for COVID-19, another study found. The assessment of retail pharmacy data, published by JAMA Internal Medicine on Feb. 11, showed increases of 50% or more above prepandemic baselines in dispensing of ivermectin, chloroquine, zinc, hydroxychloroquine, vitamin C, dexamethasone, and lopinavir-ritonavir. Use of hydroxychloroquine, chloroquine, and lopinavir-ritonavir dropped after evidence of their lack of efficacy was released, but ivermectin, zinc, and dexamethasone dispensing went up with case rates in July 2020 and again in the fall. None of these drugs have been recommended for outpatient COVID-19 treatment or prevention, so “it is particularly important to emphasize to patients the benefits of therapies demonstrated in randomized clinical trials compared with medications with uncertain benefits,” the authors said.

Finally, one guideline-recommended intervention for COVID-19, anticoagulation, gained additional evidence support from a study published by The BMJ on Feb. 11. It included 4,297 patients admitted to Veterans Health Administration hospitals. Prophylactic anticoagulation was provided within 24 hours of admission to 84.4% of the patients (almost entirely subcutaneous heparin or enoxaparin). Mortality at 30 days was 14.3% in those who received prophylactic anticoagulation versus 18.7% in those who did not (hazard ratio, 0.73; 95% CI, 0.66 to 0.81). Patients who received prophylaxis also had lower rates of inpatient mortality and therapeutic anticoagulation and no increase in bleeding requiring transfusion. The authors noted that the benefit seemed to be greater among patients who weren't admitted to the ICU within 24 hours of hospital admission. “Our results provide strong real world evidence to support guidelines recommending the use of prophylactic anticoagulation as initial treatment for patients with covid-19 on hospital admission,” they said.