IDWeek 2023: Influenza Vaccination in Older US Adults Linked to Reduction of Severe Complications, Enhanced Vaccine Furthers Clinical Benefits

This article is part of our IDWeek 2023 coverage. You can find all of our newshere.

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A new study using a stochastic model to estimate the impact of influenza vaccination on severe outcomes in older adults showed a significant reduction in cardiovascular (CV), respiratory, and other complications and also that vaccination with an enhanced influenza vaccine (ie, adjuvanted) could avert the majority of influenza-related hospitalizations and deaths.

The findings are being presented during a poster session at IDWeek 2023, being held from October 11-15 in Boston, MA.

“Influenza disproportionately affects older adults due to immunosenescence, the age-related decline in immune system function, as well as the relatively large proportion of older adults with comorbidities,” wrote authors in the poster abstract.

Investigators conducted the study to examine the value of influenza vaccination by estimating the number of severe outcomes, such as respiratory and CV hospitalizations and deaths, averted through immunization of older adults aged ≥65 years in the US.

Severe hospitalizations and mortalities prevented were estimated through a decision-tree model using a stochastic approach, according to the abstract. “The incidence rates and the probability of complications used in the model were calibrated to reflect the reported US Centers for Disease Control and Prevention data,” stated researchers.

Investigators evaluated 3 key outcomes for vaccinated or unvaccinated older adults with symptomatic influenza who developed complications: hospitalization from underlying cardiovascular disease (CVD), chronic respiratory disease, and all other causes.

The analysis compared no vaccination of older adults against influenza immunization with either a standard-dose quadrivalent vaccine (IIV4) or an adjuvanted quadrivalent vaccine (aIIV4), according to the abstract.

“Rates of hospitalization and death due to CVD, respiratory disease, and other complications of influenza were estimated for a ‘no vaccination’ scenario compared with vaccination with either IIV4 or aIIV4,” noted authors. “Vaccine coverage for both IIV4 and aIIV4 was assumed to be 65%, based on estimates of coverage in the US prior to the COVID-19 pandemic.”

FINDINGS

Results showed that no vaccination of older adults would result in:

• 44 347–196 134 individuals hospitalized for respiratory complications of influenza (median, 98 794),
• 82 306–378 236 hospitalized for CVD complications (median, 190 829), and
• 135 789–533 813 hospitalized for other complications (median, 299 343).

No vaccination of adults aged ≥65 years was also estimated to result in 3193–19 996 deaths from respiratory illnesses (median, 9303), 6379–40 583 deaths from CVD (median, 17 349), and 10 051–56 806 deaths from other complications (median, 26 235). With regards to hospitalized influenza, the estimated case fatality rate was approximately 9% among unvaccinated persons, according to researchers.

In addition, compared with no vaccination, data showed that the use of IIV4 would result in a reduction of 19 584–254 794 hospitalizations, across all 3 outcomes, and 1 517–27 548 deaths. Incremental differences between both vaccines estimated additional reductions in hospitalizations from aIIV4 vs IIV4 of 1 071–18 388 and 85–1944 deaths across the 3 outcomes evaluated.

“This analysis provides an insight into the potential impact of influenza vaccination in reducing cardiovascular, respiratory, and other complications of influenza in patients aged ≥65 years with underlying chronic conditions,” wrote investigators. “In addition, the results of this analysis show that influenza vaccination with an enhanced vaccine, such as the adjuvanted influenza vaccine, could avert the majority of hospitalizations and deaths. This research underlines the important impact seasonal vaccination can have in reducing the burden of influenza in this vulnerable population.”

Source: The value of influenza vaccination in the older adult population. A stochastic model estimation of the benefit of vaccination to prevent the severe outcomes in the U.S. Abstract presented at IDWeek; October 11-15, 2023; Boston, MA.

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