PROS1 and infection: As egg yolk IgY can be produced quickly (5 weeks of immunization period) with high yield (40-80 mg per egg) [40], neutralizing IgY has unique advantages as a potential passive immunization therapy for infections by new pathogens, e.g., SARS-CoV-2 with a new mutated form of S protein, which is possible because RNA viruses are known for their high mutation rates [41].