A little-used vaccine against bacterial pneumonia appears to cut heart attack risk in half, Canadian researchers say.

In the study of nearly 5,000 patients with an elevated heart attack risk, patients who had been vaccinated had that risk decrease by 50 per cent.

The study, to be published this week in the Canadian Medical Association Journal, found the vaccine to be most protective two years after vaccination.

The study "could mean that we may end up being able to prevent many heart attacks with a vaccine," lead study author Dr. Francois Lamontagne, of McMaster University in Hamilton, Ont., told CTV News.

The vaccine fights off Streptococcus pneumoniae, an infection that can lead to pneumonia in older adults.

The vaccine is currently recommended for people over the age of 65 and for those who have chronic diseases, such as diabetes and heart disease.

However, the vaccine could be offered to a much broader segment of the population, according to Lamontagne.

He said it is still unclear how the vaccine works to lower heart attack risk.

It may be that it reduces the risk of infections that contribute to plaque build-up in the arteries, which can cause heart attacks.

The vaccine may also offer protection against plaque by boost the immune system.

In a commentary published with the study, Dr. Mohammad Madjid from the Texas Heart Institute speculated that the vaccine lowers heart attack risk by warding off pneumonia, which is known to trigger heart attacks.

Other research has linked respiratory infections, such as influenza, and urinary tract infections with heart attack.

The findings still need to be replicated in other studies, Lamontagne said.

For now, the research suggests that physicians should increase influenza and pneumonia vaccination among high risk patients, Madjid said.

With a report from CTV medical specialist Avis Favaro and senior producer Elizabeth St. Philip


Abstract:

Pneumococcal vaccination and risk of myocardial infarction

Fran�ois Lamontagne MD MSc, Marie-Pierre Garant PhD, Jean-Christophe Carvalho MD, Luc Lanthier MD MSc, Marek Smieja MD PhD, Danielle Pilon MD MSc

Background: Based on promising results from laboratory studies, we hypothesized that pneumococcal vaccination would protect patients from myocardial infarction.

Methods: We conducted a hospital-based case-control study that included patients considered to be at risk of myocardial infarction. We used health databases to obtain hospital diagnoses and vaccination status. We compared patients who had been admitted for treatment of myocardial infarction with patients admitted to a surgical department in the same hospital for a reason other than myocardial infarction between 1997 and 2003.

Results: We found a total of 43 209 patients who were at risk; of these, we matched 999 cases and 3996 controls according to age, sex and year of hospital admission. Cases were less likely than controls to have been vaccinated (adjusted odds ratio [OR] 0.53, 95% confidence interval [CI] 0.40-0.70). This putative protective role of the vaccine was not observed for patients who had received the vaccine up to 1 year before myocardial infarction (adjusted OR 0.85, 95% CI 0.54-1.33). In contrast, if vaccination had occurred 2 years or more before the hospital admission, the association was stronger (adjusted OR 0.33, 95% CI 0.20-0.46).

Interpretation: Pneumococcal vaccination was associated with a decrease of more than 50% in the rate myocardial infarction 2 years after exposure. If confirmed, this association should generate interest in exploring the putative mechanisms and may offer another reason to promote pneumococcal vaccination.