Frequent cold and sore throat. Problem.

During 2018-19 winters, I had eaten grilled fish a lot. Around once in a week or sometimes even twice. As a result (what I noticed), I remained immuned from basic health issues such as common fever, cold and especially soar throat infection. Just in last two weeks I didn't have fish in my diet and unfortunately I got caught by sore throat and cold. I was wondering if I can get some alternate of fish during summer so that I can keep my health better. I hate sore throat and cold. It almost takes out everything off me. Anything which can help me remain safe from common cold and sore throat. Please note that I have tried foods/fruits which boost immunity such as broccoli, citrus fruits, garlic but they don't give the solution to this problem.