Another reason to get a flu shot

[Puppycow]

Particularly if you have had a heart attack. A pretty big effect too, a 50% reduction in risk.

Flu vaccine cuts risk of heart attack for some patients

People who had a recent heart attack who got the flu shot had a 55% lower risk of having a major cardiac event.

Getting a flu shot cuts the risk of having a heart attack or stroke by more than 50% in people who have had a heart attack, a new study shows.

"We may have identified that the flu vaccine may also be a vaccine against heart attacks," says lead author Jacob Udell, a cardiologist at Women's College Hospital and a scientist at the University of Toronto.

Udell and colleagues analyzed six studies on the heart health of more than 6,700 men and women, average age 67. Half got a flu vaccine; half got a placebo shot or nothing. About a third had heart disease and the rest had risk factors such as high blood pressure, high cholesterol, diabetes and smoking.

People who had had a recent heart attack who got the flu shot had a 55% lower risk of having a major cardiac event, such as a heart attack, stroke, heart failure or dying from another cardiac cause, Udell says. "The highest-risk patient got the highest reward for getting the flu shot."

Other findings, out Tuesday in JAMA, a journal of the American Medical Association, showed that people with a history of heart disease who had a flu shot:

• Had an overall 36% reduced risk of a major cardiac event, such as heart attack, stroke, heart failure or death from cardiac-related causes, one year later.

• Were less likely to die from cardiac-related or other causes. Most deaths were from cardiac causes, Udell says.

• Were 30% less likely to have a major cardiac event with a more potent vaccine compared with a typical seasonal vaccine. The stronger vaccine or a booster shot offered more protection, he says.

Amazing. I've not had a heart attack or been diagnosed with heart disease, but I like to get a flu shot anyway. This is one more possible benefit. I'll talk to my wife tonight about scheduling one. See if I can convince her to get one this year too. I wonder if the "stronger vaccine" mentioned above is available? I've never been offered a choice before between a stronger vaccine or a weaker one.

 

[casebro]

Did they correct for the simple but major confounding of :those who get flu shots also take better care of themselves in other ways- diet & exercise frinstance?

In the quote above there was no mention of the studies being DBPC, I assume they were in clinical practice and not prospective?

 

[casebro]

So a flu shot is supposed to be as good as lipid therapy?

Are the two therapies additive, or substitutive? (better word?)

 

[phunk]

How many of those who had a cardiac event after not getting the flu shot had said event while they had the flu?

 

[jdc324]

Did they correct for the simple but major confounding of :those who get flu shots also take better care of themselves in other ways- diet & exercise frinstance?

In the quote above there was no mention of the studies being DBPC, I assume they were in clinical practice and not prospective?

It's a meta analysis of RCTs. As it says in the quote in the OP: "Udell and colleagues analyzed six studies on the heart health of more than 6,700 men and women, average age 67. Half got a flu vaccine; half got a placebo shot or nothing."

I think this might be the study: http://jama.jamanetwork.com/article.aspx?articleid=1758749 The two (larger) safety trials and two of the four (smaller) efficacy trials compared with placebo while two efficacy trials compared with no treatment.

As the trials were all randomised, I'm not sure the bias of compliance would be an issue (the people who take better care of themselves in other ways are, if the trials were properly randomised, split between the two arms of the studies) - but you could argue that the inclusion of trials comparing vaccines with no treatment might be problematic, I suppose.

They also did a secondary analysis on experimental v standard vaccines and it seems that the 'stronger' vaccine or the addition of a booster dose had greater benefits than standard vaccination. Which is what you'd expect if there was an effect of the vaccine - the greater the protection against flu from vaccination (whether it's a more effective vaccine or a booster shot) the greater the protection against AMI.

Just as an aside: there are some interesting points about the reporting of the study. The reduction in risk is reported as 55% in the media - in the paper I can see a relative risk of .45 but it appears to be in a sub-group analysis of 3 trials rather than being one of the outcomes for the 6 trials (which, incidentally, are reported in various ways including absolute risk difference and number needed to treat - as are the outcomes in the sub-group analysis). In the paper, the headline figures in the abstract are for the primary meta analysis and in the full text they give the RR, absolute risk difference and NNT. In the reporting of the paper, the headline figure comes from a sub-group analysis and they give the most impressive looking figure they can find for reduction of risk. For what it's worth, here's a quote from the results section of the abstract: "Influenza vaccine was associated with a lower risk of composite cardiovascular events (2.9% vs 4.7%; RR, 0.64 [95% CI, 0.48-0.86], P = .003) in published trials."

 

[Jodie]

If you ever had the flu you wouldn't want to ever get it again. It only took one time for me, I've had my flu shot since then for the last 15 years and have not had the flu since. I can't say the same for some of my patients who lost a child to H1N1. Flu can kill you very quickly.

 

[jdc324]

How many of those who had a cardiac event after not getting the flu shot had said event while they had the flu?

I dunno mate. Don't ask me, I'm just a bumbling charlatan.

As far as I can tell, the hundreds of people who had cardiac events in the various trials analysed (let alone the thousands of participants who didn't) didn't have samples tested for flu infection. I think (unless I've missed something) the researchers basically had info on who had a flu vaccine, who had 'major adverse cardiac events', and who died. If the only differences between the two groups were (a) vaccination status and (b) cardiac outcomes do you really need serological testing of subjects in order to draw the conclusions the authors did?

It might be worth noting that flu appears to be a trigger for acute myocardial infarction: http://jid.oxfordjournals.org/content/early/2012/10/09/infdis.jis597.short

AMI risks were significantly raised during days 1–3 after acute respiratory infection (incidence ratio, 4.19 [95% confidence interval, 3.18–5.53], with the effect tapering over time. The effect was greatest in those aged ≥80 years (P = .023). Infections occurring when influenza was circulating and those coded as influenza-like illness were associated with consistently higher incidence ratios for AMI (P = .012).