Persistent vaccine-induced immunity through the typical cold weather, high risk period, and into the subsequent seasons is important in areas with year-round influenza activity.
Influenza is a worry, especially when it strikes the youngest and oldest members of our population. In the latter group, the influenza vaccine tends to produce a less robust immunologic response. Researchers know that in older adults, immunoprotection lasts at least 16 weeks. Persistent vaccine-induced immunity through the typical cold weather, high risk period, and into the subsequent seasons is important in areas with year-round influenza activity.
A multi-national team of researchers conducted a systematic review looking for studies that examined hemagglutination-inhibition (HI) titers 6 to 12 months after vaccination with inactivated trivalent seasonal influenza vaccine. They restricted studies to those that looked at adults aged 65 or older. The researchers deemed 19 studies out of 2864 eligible for inclusion, with these studies including 2565 vaccine recipients. The results, published in the journal Vaccine, indicate that many seniors do not mount enduring responses to influenza virus vaccine.
Before vaccination, 41%—51% of the study participants had some seroprotection. After vaccination, that number rose to 75%–78%. One year later, seroprotection fell to less than 60% for all serotypes. Participants’ serum titers reverted to their pre-vaccination levels.
The researchers suggest senior residents of countries that experience biannual and year-round influenza epidemics might need a different approach than the standard dose trivalent inactivated influenza virus currently recommended as a once-yearly vaccine. High-dose influenza vaccines may be an alternative.
The researchers also reminded clinicians that senior patients’ baseline health, concomitant medications, and unique immunosenescence influence vaccine response.
Pharmacists should remember that influenza, although a winter problem in most countries, is a year-round challenge in locations near the equator. Remind elderly patients who travel to monitor influenza outbreaks in their destination locations.
Young B, Zhao X, Cook AR, Parry CM, et al. Do antibody responses to the influenza vaccine persist year-round in the elderly? A systematic review and meta-analysis. Vaccine. 2016;. pii:S0264-410X(16)31044-1.