Infuenza epidemic among a community of elderly people in spite of vaccination

Abstract

An outbreak of influenza occurred in a nursing home of 81 vaccinated elderly people. The clinical attack rate was 73%. The responsibility of an A/H3N2 strain was proved in 12 patients and 2 staff members of the 15 investigated persons. The vaccine was effective in reducing mortality but not morbidity. An antigenic drift between the wild and the vaccine strains was involved in the inefficiency of the vaccination.

Influenza Outbreak in a Well-Vaccinated Nursing Home Population in Belgium

“…The present observation shows once again that the nursing home population is not safe from an influenza outbreak, even if all residents are well vaccinated 2,3 . The effectiveness of a seasonal vaccine depends on the correspondence of its antigenic composition with circulating strains.…”

“…The effectiveness of a seasonal vaccine depends on the correspondence of its antigenic composition with circulating strains. The time between vaccination and viral contact is important: after a 6-month time lapse, vaccine immunity against influenza erodes and loses its protective effectiveness 1,2,3 .…”

Long‐Term Use of Oseltamivir for the Prophylaxis of Influenza in a Vaccinated Frail Older Population

“…Influenza outbreaks reported in residential homes for seniors may be a consequence of antigenic drift between the vaccine and circulating strains. Vaccine efficacy may be reduced because of impaired immune responses in such frail older populations 4,10 …”

“…Influenza can be a significant disease in all age groups, but older adults are at greater risk for complications following influenza infection and can experience significant morbidity and mortality 1,2 . Older persons in nursing homes are at high risk for acquiring influenza, because the infection rate can be amplified through close contacts between residents 3–8 …”

Disproportional effects in populations of concern for pandemic influenza: insights from seasonal epidemics in Wisconsin, 1967–2004

“…The virus has not previously been noted for virulence, although there is some suggestion that the recommended WHO vaccine strain only partially protected against the strain circulating in some years. 26,27 As a member of the H1N1 subtype, Singapore ⁄ 6 ⁄ 86 appeared nearly a decade after the reemergence of H1N1 into the circulating virus pool in the form of A ⁄ USSR ⁄ 90 ⁄ 77, and the majority of the individuals in the elderly cohort during the period would have been exposed in their youth to the pandemic H1N1 strain of 1918. The lack of any increase in seasonal severity in the child or general subpopulations suggests a lack of ''pandemic potential''.…”