The Efficacy of the A2/Aichi/68 Strain in Inhaled Influenza Immunisation Against the A/England/42/72 Variant

Abstract

Sickness absence attributed to influenza has recently been assessed in 1007 male manual workers immunised with inhaled inactivated vaccine and 1007 unimmunised male manual workers in the same establishment. The vaccine contained strains of B/Mass/66 and A2/Aichi/68 whereas the circulating virus was exclusively A/England/42/72. The protection rate in this trial was 47% as opposed to approximately 60% in two previous trials using the same vaccine but in which no variant was known to have been encountered. The results tended to confirm the findings of a laboratory study that protection against the variant was likely to be higher than had originally been thought.