Influenza Vaccination: Part VI

A week ago, we looked at Nichol’s 2003 paper regarding LAIV for healthy working adults. Today we will review the rest of the literature regarding the effectiveness and the economic impact of influenza vaccination for working-aged adults.

The seminal work in the literature is written by Nichol and colleagues in the October 1995 edition of JAMA. The authors use a randomized, double-blind, placebo-controlled trial in Minneapolis-St. Paul, MN during the 1994-1995 flu season. The authors found significant health benefits from the vaccination.

Rate per 100 subjects
Placebo Vaccine Δ Vaccine Effectiveness P-Value
Upper Respiratory Illness (URI) 140 105 35 25% <0.001
Days of sick leave from URI 122 70 52 43% 0.001
Physician Visits for URI 55 31 24 44% 0.004

The authors also conducted a cost-benefit analysis.

Direct Costs
Vaccination $10.00
Side Effects $0.70
Medical care avoided -$16.68
Total Direct Savings -$5.99
Indirect Costs
Work time lost for vaccination $5.84
Work loss due to side effects $1.87
Work loss avoided -$48.57
Total Indirect Savings -$40.86

This paper was one of the first to conclude that it is cost effective to vaccinate healthy working adults. The authors also found that the only statistically significant difference in side effects between the vaccinated and placebo group was arm soreness. No evidence of increased tiredness, fever, muscle aches or headaches from the vaccination was found compared to the placebo group.

In 2001, Nichol re-analyzed the cost effectiveness of flu vaccination using parameters estimates from a variety of studies and then conducted a Monte Carlo simulation. In this paper, Nichol found that flu vaccination of healthy adults was beneficial but the results were of a smaller magnitude than in her 1995 study. Cost savings from vaccinating healthy working adults was now only $13.66 per person instead of the $46.85 stated in the 1995 study.

Lee, et al. (2002) uses a decision tree framework. Even if individuals become sick more often without the vaccination, they could use an antiviral treatment to decrease the flu’s effects. Thus, not having a vaccine may not actually increase sickness incidence rates. Using previously published data regarding individuals between 18 and 50 years of age, Lee finds that vaccination and treatment with rimantadine (if infected) saves $30.97 per person compared to no vaccination and no ex post treatment. Vaccination and the use of rimantadine saves $26.36 per person compared to no vaccination and treatment with rimantadine if the person becomes infected.

Not all papers, however, agree that vaccination of healthy adults is cost effective. Influenza vaccines are only cost effective when they are well matched to the influenza virus types currently circulating in a given flu season. Using a double-blind randomized, placebo-controlled trial of Ford employees in Michigan, Bridges, et al. (2000) investigate the cost effectiveness during the 1997-1998 and the 1998-1999 flu seasons. In the 1997-1998 flu season, the vaccine was only 50% effective against the flu and thus the authors found a net cost to vaccination of $65.59 per person. In the subsequent flu season, the vaccine efficiency increased to 86%, yet Bridges still finds a net societal cost of $11.17.

  • Bridges, Carolyn B., William W. Thompson, Martin I. Meltzer, Gordon R. Reeve, Walter J. Talamonti, Nancy J. Cox, Heather A. Lilac, Henrietta Hall, Alexander Klimov and Keiji Fukuda. “Effectiveness and Cost-Benefit of Influenza Vaccination of Healthy Working Adults: A Randomized Controlled Trial.” The Journal of the American Medical Association, 2000, 284 (13), pp. 1655-1663.

  • Lee, P. Y., D. B. Matchar, D. A. Clements, J. Huber, J. D. Hamilton and E. D. Peterson. “Economic Analysis of Influenza Vaccination and Antiviral Treatment for Healthy Working Adults.” Annals of Internal Medicine, 2002, 137 (4), pp. 225-231.

  • Nichol, K. L. “Cost-Benefit Analysis of a Strategy to Vaccinate Healthy Working Adults Against Influenza.” Archives of Internal Medicine, 2001, 161 (5), pp. 749-759.

  • Nichol, K. L., A. Lind, K. L. Margolis, M. Murdoch, R. McFadden, M. Hauge, S. Magnan and M. Drake. “The Effectiveness of Vaccination Against Influenza in Healthy, Working Adults.” The New England Journal of Medicine, 1995, 333 (14), pp. 889-893.

  • Nichol, Kristin L., Kenneth P. Mallon and Paul M. Mendelman. “Cost Benefit of Influenza Vaccination in Healthy, Working Adults: An Economic Analysis Based on the Results of a Clinical Trial of Trivalent Live Attenuated Influenza Virus Vaccine.” Vaccine, 2003, 21 (17-18), pp. 2207-2217.