Does a Flu Vaccine Protect the Elderly Long Enough?

A recent study concluded that a single flu vaccine may not protect elderly patients aged > 65 years in countries with biannual and year-round flu seasons.


The flu vaccine is less protective in the elderly, and how long it protects seniors is unclear. For instance, does the vaccine last beyond a typical seasonal epidemic? That’s important to know for patients in climates where the virus activity is frequent, even year round, say researchers from National University of Singapore, Lee Kong Chian School of Medicine, and Tan Tock Seng Hospital, all in Singapore; Nagasaki University in Japan; and London School of Hygiene and Tropical Medicine in the UK.

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The researchers compared findings from 15 randomized controlled trials and 4 cohort studies that involved 2,565 patients. One of the cohort studies was designed to investigate antibody persistence in the elderly and other age groups. Another was an observational study of a booster influenza vaccine at 12 weeks in elderly travelers.

The meta-analysis data showed “robust evidence” to support the conclusion that in adults aged > 65 years, hemagglutination-inhibition antibody responses after vaccination with inactivated trivalent vaccine do not reliably persist year round. Protection began to decline from days 21 to 42 through day 360. In one analysis of the data, seroprotection fell below 60% for all serotypes by day 360. A second analysis of data revealed the same thing; by day 360, titers were similar to prevaccination levels.

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The researchers say the immunologic evidence suggests that the elderly in countries with biannual and year-round influenza epidemics would benefit from an alternative to the currently recommended annual vaccination. Newer vaccine formulations that include an immunologic adjuvant or a higher antigen dose are more immunogenic, the researchers add.

An alternative, the researchers suggest, is to vaccinate more often, such as before each season in countries with biannual epidemics.

Young B, Zhao X, Cook AR, Parry CM, Wilder-Smith A, I-Cheng MC. Vaccine. 2017;35(2):212-221. doi: 10.1016/j.vaccine.2016.11.013.

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