Vaccine valency Standardize pandemic virus vaccine to be monovalent Since 1977, WHO has recommended that influenza vaccines be trivalent, containing one type A(H3N2) virus, one type A(H1N1) virus and one type B virus.
(Vaccine valency Standardize pandemic virus vaccine; to be; monovalent; T:Since 1977)
Vaccine valency Standardize pandemic virus vaccine
to be
monovalent T:Since 1977