Scientists have observed increased incidence of heart attacks (acute myocardial infarction) and stroke during the winter months. The exact reason why this happens is not completely known. But it has been thought that it is due to cold weather or due to metabolic activity in the body or due to infection such as respiratory infection.
It has also been observed that significant increases in acute heart attacks occur during peak winter incidence of pneumonia and influenza, particularly during years dominated by epidemic of influenza A. So it is surmised that this association supports the notion that the increase heart attacks during winter months is caused by influenza rather than cold weather.
Why? The favoured hypothesis is that infection triggers atherosclerotic (the stuff that clogs the arteries) plaque to rupture and cause heart attack.
A study done in the U.K., using large database of general practice patients, found that heart attacks occurred less frequently in people who had had a recent influenza vaccination than in those who had not. But the same could not be said for pneumococcal vaccination.
If influenza vaccination does have the added benefit of reducing heart attacks, then it may be important to vaccinate early in the season.
Other studies have shown influenza vaccination within the past year was associated with a 19 per cent reduction in the rate of acute heart attack among patients aged 40 years and over. Influenza vaccination administered within influenza season was also associated with a significant reduction (20 per cent) in the rate of acute heart attack.
Similar findings by other researchers reinforce current recommendations for annual influenza vaccination of target groups, with a potential added benefit for prevention of acute heart attack and stroke in those without established cardiovascular disease.
So, how are we doing with our annual influenza vaccination programs? Which one is better – targeted high risk groups or universal vaccination program?
In 2007, Statistics Canada said that despite increases in influenza vaccination rates across the country, the rates for high-risk groups are falling short of national targets.
Ontario, which since 2000 has provided free flu shots for residents aged six months and older, led the provinces, with vaccination rates rising from 18 per cent to 42 per cent between 1996/97 and 2005. Newfoundland and Labrador, with a 22 per cent rate in 2005, ranked lowest. Nationally, the rates of influenza immunization increased to 34 per cent in 2005.
In 1993, a national consensus conference on influenza set target vaccination coverage rates of 70 per cent for adults aged 65 or older and for all adults with chronic medical conditions. These targets were raised to 80 per cent in 2005.
An article published in 2003, compared Alberta’s regional coverage rates of influenza vaccination among Alberta seniors during the period April 1, 1999 to March 31, 2001. The rates of immunization in the health regions varied from 30 per cent to 80 per cent (mean 70 per cent).
Their conclusion was that some parts of Alberta can do better. Under-utilization of preventive influenza vaccination in Alberta seniors is associated with increased utilization of health services for community-acquired pneumonia. The per capita vaccination cost (about 10 dollars) was small in relationship to the per capita cost of hospital care for pneumonia (about 100 dollars).
There is no doubt that in the elderly, vaccination against influenza is associated with reductions in the risk of hospitalization for heart disease, cerebrovascular disease and pneumonia or influenza. The vaccination also reduces the risk of death from all causes during influenza seasons. So, get yourself immunized today.
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