Mar 13, 2026
3 min read
Brigham General's massive study results call for more research into the link between vitamin D supplementation and long-term COVID-19.
The results of the Mass General Brigham study are immediate for further investigation into the relationship between vitamin D supplements and long-term COVID.
In a large randomized trial, researchers at Mass General Brigham found that a high dose of vitamin D3 did not reduce the severity of the COVID-19 infection, but it may affect the long-term consequences of COVID-19.The results of the study are published in the Journal of Nutrition.
"There has been tremendous interest in whether vitamin D supplementation can be helpful in COVID, and this is one of the largest and most robust randomized trials on this topic," said JoAnn Manson, MD, DrPH, of Brigham General's Department of Mass Medicine."While we did not find that high-dose vitamin D reduced the severity of COVID or hospitalization, we observed a promising signal for long-term COVID that warrants additional research."
Vitamin D is thought to promote immune health, but clinical evidence against COVID-19 is mixed. The Vitamin D for COVID-19 (VIVID) trial aims to provide clarification by rigorously evaluating the use of high-dose vitamin D3 supplementation in patients newly diagnosed with COVID-19 and their family contacts. In the United States and Mongolia, 1,747 adults who had recently tested positive for COVID-19 and277 household contacts were randomly assigned to receive vitamin D3 (9,600 IU daily for two days, then 3,200 IU daily) or a placebo daily for four weeks. The US trial ran from December 2020 to September 2022 and the Mongolian trial ran from September 2021 to April 2022. The median time between participants testing positive for COVID-19 and starting vitamin supplementationD or placebo was three days.
Along with Manson, lead authors Dvasambu Janma, Caitlin Cook, and their team used randomization and statistical weighting to ensure that factors that could influence Covid-19 outcomes (including age, gender, body mass index, race/ethnicity and Covid-19 vaccination status) were balanced between the two groups.
Rates of health care use (including hospital, in-person or virtual clinic visits, and emergency visits) or death did not differ between the vitamin D and placebo groups over four weeks.Similarly, no significant differences were found in symptom severity.Taking higher doses of vitamin D did not reduce the rate of COVID-19 infection in the household.
However, an analysis of participants who followed the vitamin D regimen showed that they were less likely to experience prolonged symptoms of COVID after eight weeks than those who took the placebo pills.In the vitamin D group, 21% reported at least one persistent symptom, compared with 25% in the placebo group, a difference bordering on statistical significance.
"Long-term COVID-19, which can include symptoms such as fatigue, shortness of breath, brain fog, and other cognitive challenges, continues to have a significant impact on people's lives," Manson said. "We hope to conduct further research in a larger population to understand whether long-term vitamin D supplementation can reduce the risk and severity of long-term COVID-19 infection."
Authors: In addition to Manson and Ganmaa, Mass General Brigham’s authors include Allison Clar, Michael Rueschman, Aditi Hazra, Howard D. Sesso, Valerie E. Stone, Patricia Copeland and Georgina Friedenberg.Additional authors include Cook, Polyna Khudyakov, Dorjbal Enkhjargal, Tsolmon Bilegtsaikhan, Kenneth H. Mayer, Raji Balasubramanian, Douglas C. Smith, Quanhong Lei, Todd Lee, Emily G. McDonald, Tserenkhuu Enkhtsetseg, Erdenebatar Sumiya, Yansanja Navranja, Yansav YansavTserendagva, Rikard Landberg, Niclas Roxhed and Susanne Rautiainen.
Disclosures.All other authors declare no conflicts of interest.
Funding: This study received anonymous foundation support and philanthropic support from Joan Sabes, Minneapolis, MN. The authors also acknowledge the support of Tishcon Corporation, which donated the study vitamin D capsules and placebo;Takeda;and captain's cards.The authors declare no specific grant for this research from any funding agency in the public, commercial or non-commercial sectors.
Important Works: Ganmaa, D., et al."A randomized trial of vitamin D supplementation and clinical outcomes in COVID-19 and long-term COVID-19: the VIVID Trial."Journal of Food.DOI: 10.1016/j.tjnut.2026.101398
