Why You Really Need A Flu Shot (Even Though The Vaccine Isn't Great)

By Richard Knox

This flu season is shaping up to be a bad one. And this year’s vaccine doesn’t work very well against the most common flu virus going around. So should you even bother getting a flu shot?

Yes. Putting it a different way: My wife, my daughters and I will. And the evidence says you’d be somewhere between slightly foolish and dangerously blasé if you don’t — depending on your personal risk factors.

I know there are naysayers — the Internet is full of them. “I recommend that my patients of all ages not take these incessantly promoted immunizations, primarily because of their lack of effectiveness,” writes blogger Dr. John McDougall. He says he’s not one of those across-the-board vaccine deniers but just doesn’t think flu vaccines (of any given year) are worth taking.

To understand why I think he’s wrong — even this year, when vaccine effectiveness is expected to be even lower than usual --- you need to know something about the situation we’re all in.

Several viruses circulate during any given flu season. And flu viruses are always changing — sometimes not so much from year to year; sometimes in a bunch of little ways (a phenomenon called genetic “drift”); and sometimes in a big, sudden way, called a “shift,” which touches off pandemics.

Drifts Or Shifts?

Public health researchers constantly monitor flu virus mutations. But even the smartest flu dudes can’t know in advance when they’ll happen, or whether mutations will be drifts or shifts.

This year, one of the flu viruses outwitted them. Or, since viruses can’t have intentions, it’s better to say that random genetic drift in that viral strain, called H3N2, happened in late March. That’s a bad time in the annual cycle of vaccine production.

Just a few weeks earlier, leading flu specialists gathered at the World Health Organization in Geneva and decided that this season’s vaccine (for the Northern Hemisphere) should contain the same viruses as last year’s — two type-A viruses (an H1N1 that caused the pandemic of 2009 and has stuck around since, and an H3N2 that first appeared in Texas two years ago) and two type-B flu viruses.

Late-Breaking Mutant

Making each year’s flu vaccine is a complicated business that waits on no virus. The recipe has to be decided in February to get the chosen viruses growing in hundreds of millions of special chicken eggs, the first step in vaccine production.

(There is a streamlined, egg-free flu vaccine production method, but so far only one U.S.-based factory uses it.)

When the mutant H3N2 popped up in late March, there were very few of them around and it wasn’t clear whether they were going to elbow aside the previous H3N2 strain.

By September, half of the flu viruses circulating in America were H3N2s — displacing H1N1 as the dominant strain. And half of those were the drifted H3N2 mutant that’s a poor match for the current vaccine.

But by then, this season’s flu vaccine was already out. “Essentially, the flu change was too late for the vaccine to be changed,” Dr. Thomas Frieden, director of the Centers for Disease Control and Prevention, said in a recent teleconference with reporters.

So the current vaccine won’t protect very well against the dominant flu strain most Americans will be exposed to, Frieden says.

More Complications

There’s yet another wrinkle. H3N2 viruses generally make people sicker than H1N1 strains. "This H3N2 strain historically has produced more serious illness," infectious disease specialist William Schaffner of Vanderbilt University said in an interview. That means more will get complications such as pneumonia that require hospitalization and intensive care. And predictably, there will be more deaths from flu – a toll that ranges widely from year to year, from 3,000 to 49,000 fatalities.

“So that’s a double whammy — a rogue flu strain and it’s of the more severe type,” Schaffner says.

He’s also worried because this flu season has started on the early side. All but 10 states are reporting flu cases, and it’s already widespread in Maryland, North Carolina, Florida, Illinois, Louisiana and Alaska.

As all experts agree, even the best flu vaccines — those most closely matched to the viruses people will be exposed to — aren’t very good, compared to those against other infections.

The CDC says last year’s vaccine (considered a good match) was 47 percent to 56 percent effective for children and adults under age 65. Older adults don’t have such a robust immune response to vaccines, so last year’s flu vaccine was only 39 percent effective for them.

“Effective” means the percent of vaccinated people who don’t get sick. So people who got last season’s well-matched vaccine still had a 44 to 61 percent chance of getting the flu anyway — not great odds.

Tell Me Why, Again?

So why, you’re wondering, should I get a flu shot?

Here’s the argument:

•Flu is so common that even a mere 30 percent reduction in illness (or less) adds up to a lot of people. Last season, the CDC reports around 35.4 million Americans got the flu — 1 out of every 9 people. This season the misery is likely to affect millions more. There’s a good chance one of them might be you.

•Getting the flu can be more dangerous than you might think. The CDC says last year’s H1N1-dominant flu season saw nearly 400,000 hospitalized. This year the total could be substantially bigger. So could the death toll.

•Flu vaccination has both direct and indirect effects. It directly reduces the vaccinated person’s risk of getting sick, by some degree. And it indirectly lowers their chance of getting infected from someone else who got vaccinated. "You're a better citizen because you will help protect those at work and at home," Schaffner says. "No one wants to be a flu spreader."

•To me, the most compelling argument is that even if vaccination doesn’t prevent you from getting sick, you’ll probably get a milder case. So you’ll be less likely to be hospitalized or die from flu complications.

The evidence is not iron-clad. One 2010 study found that active-duty military personnel who got flu shots were 42 percent less likely to get the flu, but 62 percent less likely to get a severe case.

A German study from 2012 suggests vaccination lowers the risk of being hospitalized for flu.

We need better evidence, but given the half-million or so hospitalizations and 50,000-plus deaths we might expect from flu this year, I’m not inclined to wait for it — not when the possible means of avoiding dire outcomes is as safe, simple, cheap and available as a flu shot.

Dr. Ben Kruskal agrees. He’s chief of infectious diseases for Harvard Vanguard Medical Associates, which cares for 450,000 people in Greater Boston.

“The million-dollar question is: Does flu vaccine not only prevent us from getting this really annoying illness, but does it prevent us from dying?” Kruskal says. “The data aren’t great. But they’re good enough to get me to immunize myself and my family and to strongly recommend it to patients.”

Remember Antivirals

Important postscript: If you think you’re coming down with the flu in the weeks ahead, and you’re hearing that flu is prevalent in your community, ask a doctor or other health provider if you should be taking one of the two antiviral drugs approved for flu — Tamiflu or Relenza.

Those drugs can lower the risk of flu complications. But they need to be started within 48 hours of the first flu symptoms.

Antivirals are especially important if you’re at high risk for flu complications because you’re over 65; have chronic health conditions such as asthma, diabetes, heart, lung or kidney disease; or if you’re a pregnant woman. Children under 5, and especially those under 2, are also at high risk.

And how do you know if you have the flu versus a common cold?

“Flu invariably gives you a fever,” Vanderbilt’s Schaffner says. “You feel very crummy, weak, lose appetite, may get muscle aches and a dry, persistent cough. Beyond anything else, there’s the sense that this is worse than a common cold.”

If this feels like you, and you know there’s flu in your vicinity, get thee to a physician.

Richard Knox Senior Correspondent, CommonHealth
Richard Knox is a senior correspondent for WBUR's CommonHealth.



More from WBUR

Listen Live