Influenza vaccine: the effects of the 1986/1987 viral strains

One hundred and twenty healthy volunteers were recruited for a study to evaluate the reactogenicity and serological response of differing doses of the 1986/87 World Health Organization-recommended influenza viral strains. Each vaccine was prepared by Institut Merieux and contained A/Mississippi/1/85, A/Chile/1/83 and B/Ann Arbor/1/86. One vaccine was formulated as a 10/10/10 micrograms HA and the other as a 15/10/15 micrograms HA. No significant advantage could be found with the 15/10/15 micrograms HA combination and it was recommended, therefore, that a 10/10/10 micrograms HA formulation was to be preferred. This vaccine demonstrated a minimal cross-sensitivity to the A/Singapore/6/86 influenza strain. In view of the prevalence of the A/Singapore strain, a second study was subsequently undertaken with a monovalent A/Singapore/6/86-like vaccine in a further 62 volunteers. This demonstrated an overall sero-conversion rate of 90%. Local side-effects with both vaccines were lower than in a similar study in 1984 and this may reflect a reduction in endotoxin levels achieved by a minor modification in the manufacturing technique. These studies confirmed the efficacy of a trivalent A/Mississippi, A/Chile, B/Ann Arbor influenza vaccine and the efficacy of, and necessity for, an additional A/Singapore vaccine.