Abstract

During the summer months an influenza A2 virus isolated in Hong Kong and Singapore was shown to be antigenically sufficiently different from all other A2 strains that many people in Britain probably have little immunity against it. So far relatively few cases of influenza of this strain have occurred in Britain, but the World Health Organisation forecast large outbreaks in the Northern Hemisphere this winter,¹ and these are now occurring in the United States. A vaccine against the A2 Hong Kong strain has been prepared with remarkable speed and some has been available since October, but supplies are still short.