By Annette M. Boyle
MINNEAPOLIS—When the high dose (HD) trivalent influenza vaccine gained approval in 2009, it appeared to solve a long-standing conundrum for older patients. Patients over the age of 65 face an increased risk of severe complications and death if they contract influenza, but they mount a less robust immune response to the standard dose (SD) vaccine.
In short, the people who need immunization the most derived the least value from it.
For the VA, the reduced effectiveness of the standard dose influenza vaccine in elderly patients is particularly problematic because of the higher average age and comorbidity burden of veterans who receive care in the healthcare system. Each year, influenza sends an estimated 10,674 veterans to emergency departments according to a recent study in PLOS One.1 About 2,500 veterans require hospitalization as a result of infection with the disease, and more than 5,500 deaths are attributed to influenza annually.
The HD vaccine delivered on its promise, but questions remained. “A previously performed large, clinical randomized trial of more than 31,000 persons showed that the HD influenza vaccine was more effective than the SD influenza vaccine in preventing influenza in adults greater than 65 years” of age, said Anjum Kaka, MBBS, of the Minneapolis VAMC.
Other high-quality studies have shown that the HD vaccine was 24% more effective in preventing influenza and also was more effective than the SD vaccine in reducing hospitalizations, emergency department visits and deaths associated with influenza, according to the researchers.
Kaka and her Minneapolis VA colleagues Gregory Filice, MD, Sharon Myllenbeck, RN, and Kristin Nichol, MD, wanted to determine whether that increased effectiveness came with a significant increase in side effects among elderly patients. In their study, published in Open Forum Infectious Diseases, they noted that a prelicensure clinical trial had found that the HD vaccine had higher rates of local and systemic symptoms. Concerns about reactions might be keeping veterans who could benefit from the HD vaccine from receiving it—or they might be rightly reluctant to increase their risk of serious adverse effects.2
The team found that the HD vaccine does produce side effects at a somewhat higher rate than the SD vaccine, although mild to moderate local reactions that last less than 48 hours account for most of the increase.
“Our study, which was consistent with prior studies, showed that the risk of a severe side-effect with either influenza vaccine was low and no different between vaccines. The rate of a severe side effect in both HD and SD influenza vaccine recipients was less than 1.5% with less than 1% of individuals seeking medical attention [for side effects],” Filice told U.S. Medicine.
Looking at which patients had the most side effects, however, revealed a potential benefit from the reduced immune response seen in older patients.
“Individuals 65 to 74 [years old] had more side-effects compared to individuals over age 75 in our study. We hypothesize that this difference in side effects by age may be due to the strength of the immune response to the vaccine waning with age. A weaker immune response in older adults may lead to less local swelling and redness,” Nichol explained.
The researchers surveyed patients over the age of 65 who received influenza vaccinations October 27-29, 2015 at walk in vaccination clinics conducted by the Minneapolis VA Health Care System. While the Minneapolis VA actively encouraged elderly patients to receive the HD vaccine, a shortage of the vaccine created an opportunity to compare the side effects of the SD and HD vaccines. For 1.5 days of the three days the clinics operated, no HD vaccine was available, so all patients received the SD vaccine. Patients who arrived during the latter half of the clinic programs could choose between the SD and HD vaccines.
Starting in late November, researchers surveyed 1,088 individuals who received vaccinations at the clinic. Of those, 547 received the HD vaccine and 541 the SD vaccine.Only 5% of HD and 4% of SD respondents indicated any change in their overall health in the week following the vaccines, but 37% of the HD recipient and 22% of the SD recipients reported either a local or systemic side effect during that time period. An increased number of individuals reporting arm soreness in lasting less than two days in the HD group accounted for nearly all of the difference.
Seven of the HD recipients and three of the SD vaccine recipients indicated that they experienced a severe local or systemic side effect, but the two groups had no significant differences in their healthcare visits due to side effects. When analyzed by baseline health or presence of a high-risk condition, the vaccines had no difference in local or systemic side effects.
“We believe these results are reassuring as to safety and tolerability of the HD influenza vaccine,” said Kaka. “Given previous studies that show that the HD vaccine is superior to the SD vaccine in adults over age 65 in preventing influenza, we believe our study supports the current CDC recommendations of the HD vaccine being a reasonable choice for vaccinating” these adults.
The U.S. Centers for Disease Control and Prevention do not recommend one vaccine over the other for elderly patients.
Based on the results of the study, “We believe that the decision as to what influenza vaccine the patient should receive should be made in partnership with patients; a shared decision that balances the benefits and harms of HD and SD influenza vaccine with patient values,” said Myllenbeck.
- Young-Xu Y, van Aalst R, Russo E, Lee JKH, Chit A. The Annual Burden of Seasonal Influenza in the US Veterans Affairs Population. PLoS ONE. 2017;12(1): e0169344.
- Kaka AS, Filice GA, Myllenbeck S, Nichol KL. Comparison of Side Effects of the 2015-2016 High-Dose, Inactivated, Trivalent Influenza Vaccine and Standard Dose, Inactivated, Trivalent Influenza Vaccine in Adults ≥65 Years. Open Forum Infect Dis. 2017 Jan 12;4(1):ofx001.