A distinct reaction following a flu shot, which affects perhaps 3 or 4 people out of every 100 who are vaccinated, frequently occurs again when they’re re-vaccinated.

As many as one third of people who experience so-called oculorespiratory syndrome (ORS) following flu vaccination, have a recurrence after repeat vaccination, Canadian researchers report. However, re-vaccination of these individuals appears to be safe.

Symptoms of the syndrome include red eyes, cough, wheeze and facial swelling, Dr. Gaston de Serres of the Institut National de Sante Publique du Quebec and colleagues note in the November issue of the Archives of Internal Medicine.

The condition was first noticed in the winter of 2000-2001 in Canada, and seemed to be linked to a particular manufacturer’s vaccine.

The symptoms suggest that people are allergic to the vaccine but that’s not the case, de Serres told AMN Health. “ORS is not an allergic reaction and people previously affected by ORS do not develop an allergic reaction upon revaccination,” he stressed.

To look into the recurrence of this condition, the researchers conducted a trial in which previously affected patients were given a flu shot and a placebo injection a week apart, in random order.

Those involved were 46 patients who had ORS in 2000 and were not revaccinated in 2001, 50 patients who had ORS and were revaccinated in 2001, and 50 patients who had ORS in 2001, but not in 2000.

Half of the subjects were given Fluviral S/F, made by Shire Biologics, and the other half were given Vaxigrip from Aventis Pasteur.

Thirty-four percent of those who were given Fluviral S/F showed ORS symptoms within 24 hours of vaccination. In patients given Vaxigrip, 15 percent had symptoms.

Recurrence rates were twice as high in patients who had had ORS in 2000 and had not been revaccinated in 2001 as it was in the other two groups. Those who were given Fluviral S/F were at highest risk.

Nevertheless, the team points out that most reactions were mild, and 94 percent of patients said that they were willing to be vaccinated again in the upcoming year.

Thus, de Serres concluded, “given the mildness of ORS recurrences, people previously affected by ORS can be safely revaccinated and their physician should encourage their influenza revaccination.”

SOURCE: Archives of Internal Medicine, November 2004.