When I was reading it in the spring I was skeptical for exactly those reasons, but it quickly became clear with even the smallest bit of research that it was well accepted the Vitamin D deficiency was linked with worsened effects from common viruses and that the vast majority of people in my region were deficient.
Most of the people I've seen mentioning it recently have been medical and scientists on other sites.
Most of the people I've seen mentioning it recently have been medical and scientists on other sites.