Serum IgG subclass responses of humans to inactivated and live influenza A vaccines compared to natural infections with influenza A.

Studies with various viral agents have suggested that a preferential production of IgG subclasses may occur during infection, but limited information has been reported on the IgG isotypes produced during vaccination with live or killed virus preparations. The serum IgG subclass responses to influenza A infection or inoculation with live or killed influenza A vaccines were examined by an enzyme-linked immunosorbent assay, and results were expressed using a 4-parameter logistic model. It was observed that IgG1 was induced by both natural infections and the live virus vaccine depending on the dose given. Inactivated vaccines induced significant titres of IgG1, IgG2, and IgG3 isotypes in vaccinees, again depending upon the amount of virus preparation administered.