First ever double-blind randomised trial of Vitamin D for the prevention of Covid infections

We should be looking at prevention as well as cure

A recent paper describes the first ever double-blind randomised trial of Vitamin D for the prophylaxis of Covid.

HART has been one of many voices previously highlighting the evidence for the role of Vitamin D deficiency in preventing severe outcomes from Covid infections, and questioning why the very safe and cheap measure of ensuring adequate intake was being ignored.

The new paper outlines a study conducted in healthcare workers in Mexico.  They randomly allocated subjects (who were only eligible if they had not had covid)) to receive either 4000 IU of Vit D or placebo. The data from 94 Vit D recipients and 98 who received placebo, were included in the per-protocol analysis.

The double-blind study was conducted in late 2020, thus removing vaccination as a possible confounding factor. Covid infection was confirmed by the presence of a positive PCR test following swab testing performed at several time points during the follow-up period, or by positive antibody testing at day 45.

The results are quite extraordinary, demonstrating a highly statistically-significant 78% reduction in becoming infected if a member of the Vit D prophylaxis group; 6 out of 94 Vit D recipients caught Covid, compared to 24 out of 98 on placebo. Notwithstanding that the trial was conducted during a period of high prevalence, the rate of infection in the placebo groups seems high, although the trial was of healthcare workers, and nothing suggests the comparison between the 2 groups is invalidated by the apparent high rate of infection.

One particularly notable observation from the data is that the effect was seen regardless of whether the baseline Vit D level indicated deficiency or not, possibly indicating that the optimal minimum for Vit D levels might be higher than currently thought.

Several criticisms and open questions about the study can be posed. In particular, the study was (obviously) not powered to detect any effects on the incidence of severe disease, and the clinical relevance of preventing infections per se, when, regardless of vaccination status, infections appear to be a prerequisite for full, flexible and durable immunity, must be questionable.

Nevertheless, the study is notable for being randomised and double-blind, and for the magnitude of the observed effect.  It integrates into the body of knowledge which is building in relation to the role of Vit D in optimal immunity, and as such supports HART’s contention that willfully ignoring the potential for reducing the burden of Covid on our society with this safe, cheap and simple measure has been nothing short of scandalous.

A detailed thread critiquing some aspects of the study can be seen here

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