Influenza vaccination and asthma - Current studies and recommendations

Influenza is an important epidemic and pandemic illness associated with ser ious morbidity and mortality in unprotected communities. Patients at increa sed risk of infection are those with pre-existing cardiopulmonary disease i ncluding asthma. The influenza virus has the ability to produce antigenic c hanges posing problems for vaccine development. Influenza vaccines have been available for over 50 years. Despite the conti nuing global threat posed by infection and recommendations in many countrie s that immunisation should be widely given, uptake rates are variable and o ften poor. It has been demonstrated that infection with influenza and other respiratory viral pathogens can produce exacerbations of asthma throughout the age groups. Despite this, vaccine uptake rates in asthmatic population s are quite low. Poor uptake rates are attributed to a number of factors an d we review the evidence for the widely held view that influenza vaccinatio n produces exacerbations of chronic airflow obstruction including asthma. O bservational studies have found conflicting results: some post immunisation changes in bronchial hyperreactivity and increased requirements of broncho dilator therapy have been in some, but not all, studies. Placebo-controlled trials have not demonstrated any clinical deterioration although one study showed a small reduction in peak expiratory flow rate. Intranasal administ ration of cold-adapted live vaccines and new nucleic acid vaccines are brie fly considered. Live adapted vaccines have been shown to be effective in in fluenza immunoprophylaxis and limited data on their use in patients with as thma suggest that they can be administered safely. In conclusion, based up on current studies and evidence, it seems likely th at influenza infection produces morbidity in patients with asthma but that any potential adverse effects of influenza immunisation are outweighed by t he benefits in this population. However, placebo-controlled trials are few and only small numbers of asthmatic patients have been investigated.