Does influenza vaccination exacerbate asthma?

A few anecdotal reports have described serious asthma exacerbations following influenza vaccination. However, a causal relationship has not been clearly established since the vaccine is administered at the time of year when the background incidence of asthma exacerbation is high. Some reports describing minor pulmonary function changes or increased bronchial reactivity in patients with asthma receiving influenza vaccination did not include placebo controls and the results as they are reported are difficult to interpret. Results from several placebo-controlled studies, open trials, and US and European postmarketing surveillance data have shown no evidence of asthma exacerbation related to killed influenza vaccination, although 1 recent placebo-controlled study demonstrated a decrease in peak flow in a small number of first-time vaccinees without clinical exacerbation of asthma. A recent report demonstrated that a group of children with acute asthma exacerbation tolerated influenza vaccination to the same degree as patients with stable asthma. Thus, a plethora of evidence indicates that killed-subunit influenza vaccination is well tolerated and does not exacerbate asthma to a clinically significant degree. Limited experience with live influenza vaccine also suggests that it may be safely given to patients with asthma. Although vaccine efficacy has not been unequivocally demonstrated in patients with asthma, the potential benefits from prevention of morbidity associated with influenza infection in these patients outweighs the theoretical concerns over the safety of influenza vaccination.