Indication: Flu vaccine booster

Source: Canadian Medical Association Journal, July 2003;169(2).

Research: Researchers evaluated the effect of an oral dietary supplement derived from the edible microalga Chlorella pyrenoidosa on immune re­sponse after influenza vaccination. Researchers conducted a randomized, double-blind, placebo-controlled community-based clinical trial in a convenience sample of 124 healthy adults at least 50 years of age randomly assigned to receive the study product (200 or 400 mg of a Chlorella-derived dietary supplement) or placebo. Participants took the study product or placebo once daily for 28 days. On day 21, researchers administered a single dose of a licensed trivalent, inactivated influenza vaccine then obtained serum specimens to measure hemagglutination inhibition titres before and 7 and 21 days after vaccination. The primary immunological outcomes were the proportion of participants with a 4-fold or greater increase in antibodies and geometric mean antibody titres after vaccination; the proportion of participants reporting ad­verse events during therapy was the safety outcome.

Results: A total of 117 (94%) participants completed all aspects of the study. There were no differences in the proportions of recipients of 200 or 400 mg of the Chlorella-derived dietary supplement or placebo who achieved at least a 4-fold increase in antibodies. Reports of adverse events were similar for recipients of the supplement and placebo, except with regard to fatigue, which was reported more frequently by recipients of 200 mg of the supplement than by those who received 400 mg of the supplement or placebo. Recipients of 400 mg of the supplement who were 55 years of age or younger had significantly higher geometric mean antibody titres against influenza A/New Caledonia 21 days after vaccination and against B/ Yamanashi 7 days after vaccination; the trends were nonsignificant for titres against A/Panama. Researchers also observed similar increases for the proportions of subjects with a 2-fold or greater or a 4-fold or greater increase in antibodies. The Chlorella-derived dietary supplement did not have any effect in increasing the antibody response to influenza vaccine in the overall study population, although there was an increase in antibody response among participants aged 50–55 years. Adverse events were similar among those receiving the supplement and the placebo.