Foreword - Into the third year with COVID-19. Will gut microbiota be shown to play a role?

The third year with the corona virus daily on our retina has started. We've seen many variants of the virus. All very infectious, some apparently more life-threatening than others. Apparently, because I think it is hard to compare the number of cases during the first waves, when people were not yet vaccinated, to the current omicron wave, where clever people have had several vaccine shots. In some countries already up to 4. No matter what antivaxers say about this, all credible scientific data shows that these shots protect against the virus and although they don't stop you from getting sick, you get less sick. Most people that still end up in hospital are those that refused to get a vaccine, or are somehow compromised, e.g. because of a non-functioning immune system. Yet, still some people that have had their vaccine shots end up in the hospital. And although for antivaxers this is the ultimate proof that vaccines don't work, this of course is rubbish... (I usually use stronger phrases, but this gets printed black on white, if you know what I mean)... It would be pertinent to study why the virus breaks through the immune protection of these unfortunate people. Some believe it may be because of the microbiota. Several studies have shown a role of the gut microbiota composition in disease severity, together with vitamin D, cholesterol and other factors. Last year, it was a hype to write a `review' on gut microbiota and the effect on COVID-19, and also the board of Beneficial Microbes has received several submissions of so-called reviews on the topic. However, all of these were rejected, as they were mere speculations about how the gut microbiota might affect virus infection and diseases severity, without any data whatsoever. However, there are now some good studies out there that have shown that a proper gut microbiota may indeed influence disease severity, recently reviewed (Kim, 2021). And in small studies, certain taxa (like Bifidobacterium adolescentis) and microbial pathways (like carbohydrate metabolism) have been correlated to higher neutralising antibodies against the virus (Ng et al., 2022). Very little cause-and-effect evidence still. However, as I stated last year, it may not be too surprising for the knowledgeable reader that the microbiota plays a role in COVID, as the microbiota plays a role in everything that can be wrong with us! We just need to understand the mechanisms better to be able to make use of the microbiota for better disease outcome and perhaps even treatment.