A Measurement of Clinical Effectiveness and Cost-Effectiveness of Seasonal Influenza Vaccination in North American Population

Abstract

Background and Objectives: Emergence of resistance to anti-viral drugs spawned limited options for prophylaxis and treatment of influenza infection. Influenza cause significant morbidity and mortality among community people. Every year, influenza cause hospitalization, physician visits due to illness, complications like pneumonia and secondary bacterial infections and even deaths in pandemics. Influenza outbreaks also cause substantial increase in healthcare costs. This study was done to assess the clinical effectiveness and cost-effectiveness of influenza vaccination among community people. Methodology: This was a prospective observational study between test group (Vaccinated) and control group (Not vaccinated). Both group were followed during study period for main outcomes of the study. The main outcome measured was influenza like illness (ILI), primary care physician visits (PCP) or hospital visits for illness and any pneumonia incidence to determine the clinical effectiveness of influenza vaccination. Costs from healthcare perspective which includes cost of vaccination, cost of PCP or hospital visits, cost of medications were compared between test and control group to determine the cost effectiveness of influenza vaccination. A total of 198 subjects were enrolled in the study, 101 subjects in test and 97 in control group. ILI case definition criteria from Center for disease control (CDC) have been used for ILI cases reported. Statistical analysis was done using ‘Chi-sqare’test with P<0.05 as significance. Results: Demographics data and pre-existing medical conditions were not statistically significant between test and control group (P>0.05). There was 17.82% subjects reported general adverse reaction after influenza vaccination, which was mild to severe in intensity within 7 days of influenza vaccination. In 2013-14, the vaccine and predominant circulating viruses were well matched. Relative risk (RR) for getting influenza like illness was 0.2352 (95% confidence interval, [CI] = 0.1335 to 0.4144, P<0.01). Vaccine effectiveness (VE) was 77.00% against influenza in the current season (VE = (1- RR)×100). In the present study, Influenza vaccination reduced 38.63% of ILI, 28.03% cases of clinical influenza, 13.26% incidence of pneumonia and 40.41% of primary care physician or Hospital visits (P<0.01). Vaccination was reducing 94.40 $ from Unvaccinated to vaccinated person and total of 9534.40 $ cost savings due to vaccination of test group among study subjects. Conclusions: The “Trivalent Influenza Vaccine” of season 2013-14 is generally tolerable, clinically effective in reducing morbidity associated with disease i.e. reduce the rates of Influenza like illness (ILI), visits of Primary care physicians, visits of hospitals or emergency rooms due to ILI and other complications and incidences of pneumonia. It is also a cost-effective alternative by saving considerable healthcare costs among vaccinated group and reducing the cost from unvaccinated person to vaccinated person.