Pneumonia vaccine not only prevents bacterial infection but the injection also seems to dramatically lower the risk of heart attacks in adults, a Canadian study suggests.

Pneumococcal or pneumonia vaccination was associated with a decrease of more than 50 per cent in the rate of heart attacks after two years, Dr. Danielle Pilon of the University of Sherbrooke and her colleagues reported in Tuesday's issue of the Canadian Medical Association Journal.

The researchers compared hospital records for about 1,000 people who had suffered a heart attack with about 4,000 who did not but were at high risk for one. Participants had a mean age of about 60.

"We compared the vaccination rates of the two groups to find that the patients who did end up getting a heart attack were less likely to have been vaccinated," study author Dr. François Lamontagne said.

The researchers knew the vaccination could change one of the steps involved in atheroslerosis — the buildup of cholesterol, fat, calcium from the blood on the inside of arteries that can harden and potentially lead to heart attacks or strokes.

"The hypothesis was that if the vaccination can alter one of the steps in atherosclerosis formation, perhaps it could decrease the risk of heart attack," said Pilon. "And this is what we found."

The hypothesis that vaccination may protect against heart attacks and strokes by preventing pnemonia is a reasonable one, Dr. Mohammad Madjid of the Texas Heart Institute in Houston said in a journal commentary accompanying the study.

Pneumococcal pneumonia and other respiratory infections, such as influenza and SARS, have been shown to trigger a heart attack in some patients, Madjid noted.

Madjid suggested that doctors focus on increasing vaccination rates against pneumonia and influenza in high-risk populations, since vaccination rates are well below targets in both Canada and the U.S.

In Canada, the pneumoccocal vaccine is free, yet only 39 per cent of those who should be getting the vaccine are doing so.

Tom Mayo, 75, of St. John's has heart disease and bypass surgery to treat it. Although Mayo said he hates getting needles, he is getting the pneumoccocal vaccine, knowing that being a senior also increases his risk.

"My wife is a nurse and she keeps tabs on me, and makes sure I get needles regularly," Mayo said.

The results of the case-control study need to be confirmed, Pilot cautioned.

If the findings hold true, vaccination could go a long way to reduce heart attacks, said Dr. Chris Glover of the University of Ottawa Heart Institute. The question is, can vaccinating the general population reduce heart attacks?

"I think that's a really exciting question," Glover said.