COVID-19(54) convalescent plasma(47) Blood donors(29) SARS-CoV-2(28) positive(28) Donor(28) donors(28) conducted(27) Treatment(27) Blood(25) age(23) Blood Group(21) material(19) India(19) plasma(18) convalescent(17) neutralizing antibody(17) blood donor(17) Patient(16) Asymptomatic(15) Prospective Study(15) highest(15) IgG(15) pandemic(15) Prevalence(13) titre(13) Infection(13) COVID(13) antibody(12) COVID 19(12)