Introduction

The expanding SARS epidemic has led to cries for a vaccine to be developed as quickly as possible. This is obviously an urgent matter, but one hopes that people will be prepared to 'take a shot' more readily than they seem to be to get vaccinated against influenza. Apart from helping to avoid an unpleasant and maybe a dangerous illness, a flu shot can provide some protection in elderly people against hospitalizations for heart disease and stroke. This was reported recently in the New England Journal of Medicine.

What was done

Scientists from the US Veterans Affairs and the CDC (Centers for Disease Control and Prevention) worked together on this large study to evaluate the health of over 280,000 people over 65 during two flu seasons -1998/1999 and 1999/2000. They wanted to see whether influenza vaccination was associated with a reduced rate of hospitalization for heart disease and stroke.

Computerized data from three large managed-care organizations (HealthPartners of Minnesota, Oxford Health Plan, NY, and Kaiser Permanente Northwest) were pooled and analyzed. Baseline conditions were recorded, and then, for each flu season, hospitalizations for pneumonia or influenza, stroke, heart disease, and death from any cause. Each subject's flu vaccination status was also established.

What was found

There were 140,000 subjects in the 1998/1999 group, and 146,000 in the 1999/2000 group; 55% in the first, and 60% in the second, had been vaccinated against influenza.

At baseline, those that had received flu shots were more likely to have had medical conditions and prior hospitalizations for pneumonia. On the other hand, those who had been vaccinated were more likely to have been diagnosed with dementia or stroke.

Vaccination against flu was associated with the following benefits:

• 19% reduction in hospitalization for heart disease
• 16% (1st season) and 23% (2 season) reductions in hospitalization for stroke
• 30% reduction in hospitalization for pneumonia or flu
• 49% reduction in the risk of death from any cause

These changes were all statistically significant, i.e. they were highly unlikely to have occurred by chance alone. Of course, the high (30%) reduction in hospitalization for 'pneumonia or influenza' was to be expected, as those vaccinated obviously had a much lower chance of getting flu.

Using these results, the investigators went on to calculate how many people would need to be vaccinated to prevent one patient having a particular outcome. They found that 100 people would need a flu shot to prevent one death from any cause, and several hundreds would need a shot to prevent a heart attack or a stroke. To prevent either hospitalization or death, or both, about 65 people would need to be vaccinated.

Comment

These findings reinforce the benefits of flu shots. Smaller earlier studies have shown similar results. It's accepted that 90% of influenza deaths occur in 'the elderly'; however, the findings here have relevance for everyone over 65, and many of these folk don't consider themselves 'elderly'. What's disturbing is that this sector of the population only has a 63% vaccination rate - well below the goal of 90%.

It's possible that people are still reluctant to have a 'shot', or 'jab'. Luckily, we can expect that nasal administration of influenza vaccine is not far off - maybe it will be available in time for next year's vaccination season. After that, there will be no excuse. Although the SARS death rate is around 5%, and causing considerable alarm, it must be remembered that influenza-associated deaths in the USA run at about 50,000 per year; and 90% of these are in the over 65-year-olds, just those that aren't getting vaccinated. Obviously, the health message has not been adequately transmitted, or received, or it's been ignored.

Source

Influenza vaccination and reduction in hospitalizations for cardiac disease and stroke among the elderly.
KL. Nichol, J. Nordin, J. Mullooly,  et al., N Engl J Med, 2003, vol. 348, pp. 1322--1132

Links

• Are Flu and Pneumonia Vaccines Worth It?
• Can a Multivitamin a Day Keep Infections at Bay?
• Regular Exercise Boosts Effectiveness of 'Flu Shot