There are behaviors to avoid which weaken the immune system and behaviors to implement to strengthen it. For detailed specifics in a shareable format please see https://www.facebook.com/TheOriginalDetoxWorld/posts/2515352648678391?
Social distancing is the very best way to prevent exposure to COVID-19 in the first place but if that is not possible, good ways to increase immunity are indicated in the above answers, including maintaining good nutrition, eating "pigmented fruits and vegetables" (See answers above from Dr. Arvind Singh, Nasar Ahmed Elsawy, and others), which will supplement food intake of vitamin A, C, E, zinc, rose hips, provided by orange juice, eggs, carrots, cabbage and other legumes.
it is necessary to eat vegetable products rich in micro-and macronutrients, vitamins. With exercise, I would recommend pampering yourself (the number of lymphocytes increases).
Improve Your Diet. The food you eat plays a key aspect in determining your overall health and immunity. Eat low carb diets, as this will help control high blood sugar and pressure. A low carb diet will help slow down diabetes and focus on a protein-rich diet to keep you in good shape. And regularly consume vegetables and fruits rich in Beta carotene, Ascorbic acid & other essential vitamins. Certain foods like mushrooms, tomato, bell pepper and green vegetables like broccoli, spinach are also good options to build resilience in the body against infections. You can also eat supplements rich in omega 3 & 6 fatty acids for your daily dose, if stepping out to buy groceries is not an option during social distancing. Some natural immunity supplements include ginger, gooseberries (amla) and turmeric. Some of these superfoods are common ingredients in Indian dishes and snacks. There are several herbs that help in boosting immunity like garlic, Basel leaves and Black cumin. Certain seeds and nuts like sunflower seeds, Flax seed, pumpkin seeds and melon seeds are excellent sources of protein and vitamin E. Probiotics like Yoghurt, Yakult and fermented food are also excellent sources to rejuvenate the composition of gut bacteria, which is important for nutrient absorption by the body. These are good options for the older generation too. https://www.google.com/amp/s/www.narayanahealth.org/blog/boost-immune-system-against-coronavirus-covid-19-infection/
Don’t Compromise on Sleep. Good snooze time for 7-8 hours is the best way to help your body build immunity; lesser sleep will leave you tired and impair your brain activity. The lack of sleep will prevent the body from resting and this will impair other bodily functions that will have a direct impact on your immunity. Lack of sleep adversely affects the action of the flu vaccine. https://www.google.com/amp/s/www.narayanahealth.org/blog/boost-immune-system-against-coronavirus-covid-19-infection/
Exercise. A good diet should be followed by an exercise routine. Remember to exercise regularly; even light exercise will go a long way in releasing the toxins from your body. It is recommended to exercise for 30 to 45 minutes, depending on your stamina. If you have not started exercising yet, then it is a good time to start. There are several Youtube channels and apps to help you exercise at home. Regular exercise improves metabolism, which has a direct correlation with body immunity. https://www.google.com/amp/s/www.narayanahealth.org/blog/boost-immune-system-against-coronavirus-covid-19-infection/