Asthmatics Benefit From Flu Shots

FEBRUARY, 1998: NEW YORK (Reuters) -- The benefits of flu vaccination for asthmatic patients far outweigh the "very small risk" of developing pulmonary complications from the vaccine, say UK researchers in the January 31st issue of The Lancet.

Currently, many asthmatics are not vaccinated against flu because of fear that the vaccine itself will trigger an exacerbation of their illness. But such fears may be misplaced, Dr. Karl G. Nicholson of Leicester Royal Infirmary and coworkers say. "Colds can trigger exacerbations, which may be mistaken for vaccine-related adverse events," they write in their report.

To determine the safety of flu vaccination in asthmatic patients and determine whether having a cold could be a confounding factor in exacerbations, the UK team conducted a double-blind, placebo-controlled, crossover study of 262 patients from nine respiratory centers and two asthma clinics in various regions of the UK.

Participants received a flu or placebo injection in random order, with a two-week interval between injections.

Overall, 11 of the 255 patients who completed the study had an exacerbation -- defined as a fall in forced expiratory volume (FEV1) of greater than 20% -- after the flu vaccine compared with 3 after placebo. But when Nicholson's team excluded from the analysis patients who had a cold during the study period, no significant difference was seen in the numbers of exacerbations following vaccine or placebo, or in related parameters, such as symptoms or medication use.

Further analyses revealed that among the 97 asthmatics receiving flu vaccinations for the first time, 9 had exacerbations following the vaccine compared with 1 following placebo -- a significant difference. By contrast, no significant difference in exacerbations was seen in the 164 repeat vaccines. This suggests either that an asthmatic's first exposure to the flu vaccine is more likely than subsequent exposures to induce an exacerbation, say the researchers, or that those who have an exacerbation after a single vaccination are less likely to have another vaccination.

Either way, and despite the fact that some pulmonary abnormalities may occur as a complication of vaccination, flu itself is a much greater risk to asthmatics than is the vaccine, the authors conclude. "In practice, influenza is associated with substantial morbidity, absenteeism, medical consultations, hospital admissions, and death." Since vaccination prevents about "75% of ...influenza in working adults, influenza vaccine should prevent far more exacerbations of asthma than it causes," they conclude.

SOURCE: The Lancet (1998;351:326-331)