When people with chronic obstructive pulmonary disease (COPD) catch the flu, they're at risk for unpleasant complications. But nobody knows if giving COPD patients the flu vaccine will help, and some physicians worry that the vaccine could make their COPD worse.

What they wanted to know: Does vaccinating COPD patients against the flu protect against respiratory illness?

What they did: COPD patients who regularly came to the COPD clinic at Siriraj Hospital in Bangkok, Thailand, were recruited for the study. Each of the 132 patients was randomly assigned to get an injection of vaccine or placebo—neither the patients nor the person doing the injection knew which it was. Then the patients' acute respiratory illnesses were tracked and classified as common cold, influenzalike illness, pneumonia, or acute exacerbation of COPD (which has a complicated definition but may include more trouble breathing, more sputum, or more pus in the sputum than usual). Flu infection was determined by blood test. Only 22 patients got influenza, most in the unvaccinated group. Seven patients died or dropped out.

What they found: Patients who got the flu shot were much less likely to have influenza and the associated acute respiratory illness; four of the 62 vaccinated patients had influenza-related acute respiratory illness, compared with 17 of the 63 placebo patients. Overall, though, there were about the same number of acute respiratory illnesses in the two groups (just fewer caused by flu in the vaccinated group).

What it means to you: Getting a flu vaccine probably isn't a bad idea for people with chronic obstructive pulmonary disease.

Caveats: This was a slow year for influenza in Thailand; in a year with more flu, the differences between the groups would probably be bigger.

Find out more: Facts about COPD: http://www.nhlbi.nih.gov/

Influenza from the Centers for Disease Control and Prevention http://www.cdc.gov/flu/

Read the article: Wongsurakiat, P., et al. "Acute Respiratory Illness in Patients with COPD and the Effectiveness of Influenza Vaccination: A Randomized Controlled Study." Chest. June 2004, Vol. 125, No. 6, pp. 2011–2020.