Lower risk of respiratory-related hospitalization after high-dose influenza vaccination in the elderly
Elderly individuals residing in nursing homes had a lower risk of respiratory-related hospital admissions during the influenza season after receiving a high-dose influenza vaccine compared with a standard-dose vaccine, a recent study found.
Eight hundred and twenty three nursing care facilities in the US participated in the study. Individuals aged ≥65 years (mean age 83.6 years, 72 percent female) who had been living in the nursing homes for ≥90 days were randomized to receive either high-dose (60 µg antigen per virus strain; n=26,639) or standard-dose (15 µg antigen per virus strain; n=26,369) influenza vaccine for the 2013–2014 influenza season.
Hospital admission due to respiratory issues was lower among patients who received the high-dose vaccine compared with the standard-dose vaccine (0.185 vs 0.211 per 1,000 resident-days; adjusted relative risk [adjRR], 0.873, 95 percent confidence interval [CI], 0.776–0.982; p=0.023). [Lancet Respir Med 2017;doi:10.1016/S2213-2600(17)30235-7]
Pneumonia- related hospital admissions were also reduced among individuals receiving the high-dose vaccine compared with the standard dose (0.067 vs 0.084 per 1,000 resident-days; adjRR, 0.791, 95 percent CI, 0.267–0.953; p=0.013), as were all-cause admissions (1.021 vs 1.113 per 1,000 resident-days; adjRR, 0.915, 95 percent CI, 0.863–0.970; p=0.0028), while all-cause mortality rate was not affected by vaccine dose (p=0.57).
The reduction in all-cause admission suggests that the impact of the high-dose vaccine extends beyond that of influenza-related respiratory conditions, said the researchers.
“Establishing improved vaccine effectiveness in a nursing home population is noteworthy, considering this population typically has a reduced vaccine response because of immune senescence and multiple morbidities, and are at a high risk for being admitted to hospital for multiple reasons, in addition to respiratory illness,” said the researchers.
“[S]tandard-dose inactivated influenza vaccines ... are known to be less immunogenic in older adults than in healthier, younger adults,” commented Drs Marc-Alain Widdowson and Joseph Bresee from the US Centers for Disease Control and Prevention, in Nairobi, Kenya, and Atlanta, Georgia, US, respectively. [Lancet Respir Med 2017;doi:10.1016/S2213-2600(17)30290-4]
“[T]his study presents strong evidence that influenza has a major role in seasonal hospital admissions of older nursing home residents ... it seems that high-dose influenza vaccines can reduce this burden substantially better than a standard-dose vaccine,” they said.
However, the researchers cautioned that the main circulating virus strain during the 2013–2014 influenza season was A(H1N1)pdm09, a strain that is considered less virulent than the A/H3N2 strains, and which may have affected the findings, particularly among the elderly population.