An influenza B outbreak during the 2007/2008 winter among appropriately immunized elderly people living in a nursing home.

The study evaluated the immunogenicity and efficacy of a trivalent subunit MF59-adjuvanted influenza vaccine (A/Wisconsin/67/05 (H3N2), A/Solomon Islands/3/06 (H1N1) and B/Malaysia/2506/04) in preventing serologically diagnosed infections in a group of 67 institutionalized elderly volunteers during 2007/2008 winter, characterized by co-circulation of drifted A/H3N2, A/H1N1 and B influenza viruses. Influenza vaccination induced a significant increase in the amounts of hemagglutination inhibiting antibodies, both against the vaccine and the epidemic drifted strains. However, vaccination did not prevent the circulation of the new drifted influenza B virus (B/Florida/4/06-like), belonging to the B/Yamagata/16/88-lineage, antigenically and genetically distinct from B/Victoria/2/87-lineage viruses from which the vaccine B strain was derived.

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

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.

Influenza vaccination in patients on long-term anticoagulant therapy.

The study evaluates the risk/benefit of influenza vaccination in patients on stable long-term oral anticoagulant therapy (OAT). One hundred and four consecutive patients with indication for influenza vaccination were randomized to receive one dose of 2004/2005 influenza vaccine followed by placebo after 6 weeks, or vice versa, in a cross-over blinded trial. All patients were tested for anticoagulation levels and for hemagglutination inhibiting antibody titres against the influenza vaccine antigens. The highly protective antibody titres induced by influenza vaccination and the absence of statistically relevant interactions between vaccination and OAT suggest that influenza vaccination can be used safely and successfully in elderly patients on OAT.

An influenza A/H3 outbreak during the 2004/2005 winter in elderly vaccinated people living in a nursing home.

This study examined the antibody response against the three vaccine antigens and the epidemic A/H3N2 drift variant (A/California) and the prevention of laboratory diagnosed influenza infections in a group of elderly institutionalized people vaccinated with the 2004/2005 influenza vaccine. Antibody titres were measured by hemagglutination inhibition (HI) in sera collected before and 1 month after vaccination. Laboratory diagnosis was done examining throat swabs (RT-PCR or MDCK cell culture) or by serology (seroconversion comparing HI titres in sera collected 1 and 5 months after vaccination). Results obtained showed that influenza vaccination induced an adequate immune response against the three vaccine antigens and the epidemic A/H3N2 variant, however it was not capable of preventing an influenza outbreak due to the new A/H3N2 (A/California) variant.