This article is more than 5 years old. Information may no longer be current.
Vaccination eases influenza’s impact on work productivity
Click Here to Manage Email Alerts
Laboratory-confirmed influenza infection resulted in 45% more missed work hours and more severe illness than acute respiratory infections not confirmed as influenza, although the latter may be significantly reduced with vaccination, according to recently published research.
“Past estimates of burden, particularly in terms of lost productivity, have typically used nonspecific outcomes such as ‘acute respiratory illness’ or ‘influenza-like illness’ based on symptomatic case definitions,” Joshua G. Petrie, MPH, of the University of Michigan School of Public Health, and colleagues wrote. “With the development of real-time reverse-transcriptase PCR [RT-PCR] assays, we are now able to identify precisely those illnesses that are potentially vaccine-preventable. We can also compare the severity of illnesses laboratory-confirmed as influenza to those that are not.”
Joshua G. Petrie
Petrie and colleagues examined a cohort of 1,548 working adult patients with medically attended acute respiratory illnesses (MAARI) who participated in the U.S. Flu Vaccine Effectiveness Network study during the 2012-2013 influenza season. Those included were employed and worked 20 or more hours a week, and had RT-PCR testing, vaccination and outcome data readily available. Demographic characteristics, subjective self-assessments of health and productivity impairment information also was collected at enrollment and through a follow-up survey completed 7 to 21 days after illness. Using these data, researchers compared illness severity and hours of work missed between participants with and without lab-confirmed influenza, and between those with influenza who did and did not receive seasonal vaccination.
RT-PCR testing offers new insights
Approximately 38% of participants with MAARI tested positive for influenza, the majority of which were influenza type A(H3N2), Petrie and colleagues wrote. The mean age of the cohort was 44 years, and the majority were female and white.
MAARI cases that tested positive for influenza believed themselves to be less healthy than noninfluenza cases upon enrollment (P < .001), and reported reduced sleep quality and ability to perform normal activities as well. Influenza cases reported missing an average of 20.5 work hours due to their illness, compared with an average of 15 hours reported by those without influenza (P < .001). Median reported illness duration for both groups was 7 days.
“These findings are consistent with the results of previous studies that indicated influenza illnesses were more likely to be medically attended than illnesses caused by other respiratory viruses, and that those infected with influenza had higher illness severity scores than those with noninfluenza acute respiratory illness,” Petrie and colleagues wrote.
The impact of influenza on MAARI patients appeared to be diminished by previous vaccination, the researchers wrote, as participants with influenza were more likely than those without to have documented evidence of influenza vaccination (40% vs. 54%; P < .001). Health status reported at enrollment (P = .01) and ability to perform normal activity (P = .04) were both greater for vaccinated cases of influenza, as opposed to unvaccinated cases.
While there were no significant differences in work hours missed, productivity and duration of illness among these groups, Petrie and colleagues pointed to influenza prevention as the primary economic benefit of vaccination.
“Due to the substantial economic and personal burden of acute respiratory illnesses including influenza, there are clear benefits to be gained by effective prevention and treatment strategies,” the researchers wrote. “These findings confirm the potential value and economic benefit of vaccination and illustrate the importance of laboratory-confirmation of influenza outcomes in evaluations of vaccine effectiveness.”
Influenza vaccination reduces illness severity despite antigenic drift
Although the study published in Clinical Infectious Diseases reflects an influenza vaccine moderately matched to the circulating virus, additional data reported by Petrie at IDWeek 2015 support vaccination regardless of antigenic drift.
In his late breaker presentation, Petrie described an analysis of 642 adult patients hospitalized for treatment of acute respiratory illness at two Michigan health care institutions during the 2014-2015 influenza season. Throat and nasal swab samples were collected and tested for influenza using real-time PCR, and clinical outcomes were compared among patients who did and did not receive vaccination using logistic regression models adjusted for factors such as age, sex, hospital and Charlson Comorbidity Index.
Approximately two-thirds of the cohort were considered vaccinated, and 18% tested positive for influenza infection, according to Petrie. H3N2 was common in positive influenza samples, among which 88% belonged to the 3C.2a drifted genetic group that dominated the season. Adjusted effectiveness of influenza vaccination among these patients was 47% against all influenza (95% CI, 13%-68) and 46% against H3N2 (95% CI, 7%-68%), suggesting that the 2014-2015 vaccine provided some protection to acute respiratory patients.
“Despite the mismatch between the circulating and vaccine viruses, vaccine efficacy estimated in this study was … much higher than the 7% estimated by the [U.S. Influenza Vaccine Effectiveness Network] in the ambulatory care setting,” Petrie said during the late breaker presentation. “One potential explanation for this difference could be that the influenza vaccine may have been more effective in preventing more severe illness outcomes, such as those requiring hospitalization. However, we want to be cautious with that interpretation.” – by Dave Muoio
Reference:
Petrie JG, et al. Abstract LB-9. Presented at: IDWeek; Oct. 7-11, 2015; San Diego.
Disclosure: Petrie reports no relevant financial disclosures. Please see the full studies for a list of all other authors’ relevant financial disclosures.
Click Here to Manage Email Alerts