The concept of natural immunity is flawed. You get immune against a pathogen by being infected by this pathogen. But this doesn't help against a different pathogen. This means, that you'll be sick more often, if you're building up immunity, than if you're avoiding pathogens. May I therefore suggest to cough at refrigerated stuff? You won't get sick that way, but viruses can live forever in a fridge, so you'll be giving other people immunity. And as we all know, at least 70% of people need to get their immunity until things get better.