It's just a Letter- it carries little or no weight. And it looks like it's from a cardiologist- somebody with no deep/special knowledge of the immune system or viruses https://www.researchgate.net/scientific-contributions/Kenji-...
See the impact metrics on their main page, https://virologyj.biomedcentral.com/
it's a fairly low impact factor, meaning few people cite papers (or letters) from it.