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Gerontology. 2007;53(6):411-8. Epub 2007 Oct 31.

Effects of repeated annual influenza vaccination on antibody responses against unchanged vaccine antigens in elderly frail institutionalized volunteers.

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1
Department of Medical Surgery Specialities and Public Health, University of Perugia, Perugia, Italy. anna@unipg.it

Abstract

BACKGROUND:

Concern about the possibility that annually repeated influenza immunizationmayinduce a lower antibody response than first vaccination.

OBJECTIVE:

To ascertain the cumulative effects of yearly vaccination on serological response to unaltered vaccine antigens in the elderly.

METHODS:

The haemagglutination-inhibiting (HI) antibody response was examined in 158 elderly institutionalized frail volunteers subdivided in 3 groups according to the sequential winters in which each subject received a trivalent inactivated influenza vaccine. The study, conducted over 5 consecutive winters (from 1998/99 to 2002/03), reports the antibody response only for sequential years (2 or 3) in which the vaccine strain examined was not altered.

RESULTS:

Significant increases in the values of HI antibody titres were observed after vaccination in each year examined against the different influenza vaccine strains used, except against B antigen in the second of the 3 winters studied (1999/00). The antibody responses found were not always adequate, i.e. at levels above the currently requested values for commercial vaccines (post-vaccination seroprotection rate >/=1:40, increases in geometric mean titres >/=2, positive responses >/=30% compared with pre-vaccination), probably because of old age (mean age >/=81 years) and the presence of underlying diseases in a high percentage of volunteers (>/=86%). The most frequent chronic diseases found werecardiovascular diseases (48%), endocrine disorders (19%), functional disability (10%) and pulmonary diseases (4%). The post-vaccination values observed in the sequential years were in general similar for A/H3N2 and A/H1N1 vaccine strains. A decrease, however, for some parameters at statistically significant levels, was observed against B antigen following repeated vaccine administrations.

CONCLUSION:

Our data seem to support the possibility of a slight impairment of HI antibody response against unaltered influenza vaccine antigens, especially for influenza strains that have circulated for prolonged periods of time. Indeed a tendency to a lower response was found only against B/Beijing antigen, introduced in the vaccine composition in the winter 1995/96, but not against the A/H3N2 and A/H1N1 vaccine strains, which weremore frequently changed.

PMID:
17975317
DOI:
10.1159/000110579
[Indexed for MEDLINE]
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