Hello,
It is very likely that the cause of your recurring colds is your nephew's colds. During the first year of daycare, children get colds very frequently.
If vitamin D has preventive effects (and I say if because it has not been proven beyond doubt that vitamin D has beneficial effects in preventing respiratory diseases), it could not prevent the transmission of the cold virus if you are in close contact with your infected nephew
The same reasoning applies to BioK+. While there is some evidence to suggest that taking probiotics keeps the system alert (ready to respond), there is also no evidence that it would have a positive impact on respiratory infections
Hydrasense is a good product to eliminate excess secretions and promote better breathing. It is an interesting product to help treat congestion due to colds
To answer your question, the only validated approach to the cold virus is preventive measures (frequent hand washing, avoiding contact with infected people, good respiratory hygiene). Symptoms can also be treated when they are present and uncomfortable, but no treatment can reduce the duration of a cold or prevent it
To differentiate between the common cold and COVID-19, there are several things to consider.
The common cold is a respiratory virus and causes the symptoms we know: nasal congestion, runny and itchy nose, secretions in the throat, sometimes a headache or fever
It is now known that the coronavirus that causes COVID-19 is a multisystem virus, which means that although the most apparent symptoms are respiratory, it is not a respiratory virus only. The most common symptoms are fever, cough and difficulty breathing. There may be some early symptoms such as diarrhea or loss of smell, but only in about 10-20% of cases. Significant fatigue and body aches are more common than with the common cold