There are scientific studies showing that nose filters allow you to filter to a high degree most types of airborne particles when inhaled via your nose. Those particles may include airborne viruses including the flu-virus, coronavirus, or other viruses.
Currently, there are no official studies investigating the level of protection of nose filters specifically against viruses, including coronavirus, but there are several indirect studies that can help us extrapolate some reasonable conclusions.
In short, nose filters cannot guarantee to you 100% protection against any virus, including the flu-virus or/and the coronavirus (and frankly speaking, no honest company can make this claim for any of their products), but they could be a good additional step for you to add one more layer of protection against airborne viruses.
You can read in more detail about our evaluation of nose filters against the coronavirus here.