“…The single radial haemolysis (SRH) test (Russell, McCahon and Beare, 1975;Schild, Pereira & Chakraverty, 1975) is now widely used for the determination of antibody to influenza A and B viruses in both vaccine studies and following natural infections (Vaananen et al, 1976;Farrohi et al 1977;Delem & Jovanovic, 1978;Cretescu et al 1979;Chakraverty, 1980;Grilli & Davies, 1981;Oxford, Yetts & Schild, 1982;Yamagishi et al 1982; Goodeve, Jennings and Potter, 1983). It is a test both simple and reproducible, rapid to perform, and more sensitive than the conventional haemagglutination-inhibition (HI) test (Russel, McCahon & Beare, 1975;Oxford et al 1982;Goodeve, Jennings & Potter, 1983;Jennings et al 1984).…”