# 2527
Research at Walter Reed Army Medical Centre, Washington, DC has shown that for healthy adults, under the age of 49, that half-dose flu vaccines appear to work just about as well as full-dose vaccines.
It should be noted that research was conducted on seasonal flu strains, and it isn't clear that these results would hold true for a novel pandemic strain vaccine.
Some early pre-pandemic vaccine trials have yielded disappointing low-dose antibody responses.
Those adults receiving the half-dose vaccine saw no increase in medical or hospital visits, showed comparable elevation of antibody titers, and experienced fewer vaccine related side effects (headaches, myalgias, fatigue).
Women in all age groups saw a greater antibody response at the half dose than did men.
The research appears in the Archives of Internal Medicine.
Half- vs Full-Dose Trivalent Inactivated Influenza Vaccine (2004-2005)
Age, Dose, and Sex Effects on Immune Responses
Renata J. M. Engler, MD; Michael R. Nelson, MD, PhD; Mary M. Klote, MD; Mark J. VanRaden, PhD; Chiung-Yu Huang, PhD; Nancy J. Cox, PhD; Alexander Klimov, PhD, ScD; Wendy A. Keitel, MD; Kristin L. Nichol, MD; Warner W. Carr, MD; John J. Treanor, MD; for the Walter Reed Health Care System Influenza Vaccine Consortium
Arch Intern Med. 2008;168(22):2405-2414.
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Conclusions Antibody responses to intramuscular half-dose TIV in healthy, previously immunized adults were not substantially inferior to the full-dose vaccine, particularly for ages 18 to 49 years. Significantly higher geometric mean titer responses in women were identified for all ages, regardless of dose or influenza strain. Half-dose vaccination may be an effective strategy for healthy adults younger than 50 years in the setting of an influenza vaccine shortage.
This research opens the possibility that in years where vaccine shortages occur, full-dose vaccines could be reserved for children and the elderly, while adults under the age of 50 could receive a lower-dose vaccine.
