APPLICATION: Serum IgA antibodies appear 2-4 weeks after infection and last for 3 - 5 months. Very young babies may be unable to mount an IgA response to infection. IgA antibodies are not stimulated by vaccination. IgG antibodies appear 3-4 weeks after symptoms and may be detectable for up to 5 years.
NB This is NOT a reliable test for post vaccination immunity.