INFLUENZA VACCINES - THE EFFECT OF VACCINE DOSE ON ANTIBODY-RESPONSE IN PRIMED POPULATIONS DURING THE ONGOING INTERPANDEMIC PERIOD - A REVIEW OF THE LITERATURE

Health authorities tend to favour an increase of the antigen dose in i nactivated influenza vaccines from less-than-or-equal-to 10 mug haemag glutinin (HA) per vaccine strain to 15 mug HA / strain. The increased dose is expected to yield a meaningful increase in the number of subje cts to be protected after vaccination. To verify this expectation, we have reviewed 20 published reports (1978-1991) of serological studies in which anti-HA-IgG antibody after different doses was measured. In t he review, stratification groups of previously primed subjects were fo rmed and the antibody response was estimated for doses of 10 and 15 mu g HA by linear k2-chi2 model. Despite a considerable heterogenicity o f study populations, study designs, vaccine types and strains, and ant ibody assays, the results were consistent in revealing high protection rates (greater-than-or-equal-to 75%) for a 10 mug HA dose of influenz a A vaccine components. For both response and protection rates, an inc rease of the antigenic load from 10 to 15 mug HA was not associated wi th a meaningful increase of seroresponse: in 38 out of 39 stratificati on groups, the increase of response and/or protection rate varied betw een - 9% and + 8%, with a median of 1.5%. These results do not justify the expectation that a vaccine dose of 15 mug HA per strain would be clinically superior to a dose of 10 mug HA. Only in a group of immune- compromised patients on chronic intermittent haemodialysis were result s in favour of a higher dose found, which may justify further evaluati on in this special population.