From "Here’s How to Avoid Catching Colds and the Flu": https://time.com/4672626/vitamin-d-cold-flu/ "For the new study, a meta-analysis published in The BMJ, researchers looked at individual data from nearly 11,000 people who had participated in randomized controlled trials in more than a dozen countries. The researchers found that people who took daily or weekly vitamin D supplements were less likely to report acute respiratory infections, like influenza or the common cold, than those who did not. Those who had low vitamin D levels before they started supplementation got the biggest benefit: For people with the most significant vitamin D deficiencies (blood levels below 10 mg/dl), taking a supplement cut their risk of respiratory infection in half. People with higher vitamin D levels also saw a small reduction in risk: about 10%, which is about equal to the protective effect of the injectable flu vaccine, the researchers say. No significant benefits were associated with high doses of vitamin D spaced out over larger periods of time."

So, given this BMJ-published research, why can researchers in the article's paper get away with claiming that flu vaccines are more effective than any other option (including vitamin D supplementation) when the research suggests otherwise?