Flu shots offered only 9% protection for people over 65 against the most severe strain of flu circulating this season, the U.S. government says. That strain was the most common this season as well as the one that caused the worst illness. Overall, the vaccine provided about 27% protection against 3 strains of influenza for adults over 65, the new report said. Protection was about 56% for all age groups. The Centers for Disease Control and Prevention released the statistics February 21. Flu generally hits older adults harder, and flu shots don't work as well for them. Overall, the effectiveness of this season's vaccine was not much below average, experts told the Associated Press (AP). Because flu changes quickly, there's a lot of guesswork in creating the vaccine. So 30% to 40% effectiveness is considered good for seniors, AP said. About 60% to 70% is acceptable for all groups. But the 9% rate of protection was particularly low. Perhaps partly as a result, hospital stays for older adults hit one of the highest levels in a decade.

By Mary Pickett, M.D.
Harvard Medical School

What Is the Doctor's Reaction?

Healthy patients are satisfied customers. My patient was not happy.

"I am calling to let you know that I have the flu," she said. "And because I got the flu, I am going to get a new doctor, in another clinic."

My nurses had given this patient a flu shot several weeks earlier. She was flabbergasted that it did not work. Among her frustrations was the fact that I did not push her, a woman over 65, to get the new high-dose flu vaccine. For our older patients, there has been a fair amount of confusion and a large amount of disappointment relating to flu vaccine benefit.

Last month the Centers for Disease Control and Prevention (CDC) reported that overall, this year's flu shot is 62% -- or "moderately" -- effective. This means it is possible to get the shot and still get the flu. But the vaccine does make flu less likely.

Now the CDC has released updated information. The report says that in people over age 65, this year's flu vaccine is about half as effective as it is in the population overall. Counting all three strains in the vaccine, it is 27% effective at preventing flu. And this year's flu shot is only 9% effective in protecting our older patients against the most common strain of flu this year. That strain is also the most severe.

So which flu shot are we talking about for older patients? If you are over 65, you may have noticed that this year you could choose between two flu shots. The first is the usual "low-dose" vaccine. The second is a "high-dose" version, which also has more side effects.

The CDC report lumps both of these vaccine types together. We don't yet have clear information about whether the high-dose vaccine is more effective. Early studies suggested that it might cause a bigger immune response right after the vaccine was given. But we don't yet know whether this burst of immunity lasts through flu season and provides better protection. We do know that people getting the high-dose vaccine have had more vomiting, more fever and more pain around the site after being vaccinated.

If you are over 65, you can get the high-dose vaccine. But the CDC has not recommended one vaccine type over another. Neither has the Advisory Committee on Immunization Practices. We need more information before we know if the high-dose vaccine is a better choice.

What Changes Can I Make Now?

This year a lot of people have been walloped by the flu. And many of these people got the flu shot. That doesn't seem fair.

But don't let that talk you out of flu shots for the future. In most years, the flu shot protects against 70% to 90% of circulating flu virus infections. Five years ago in 2007-2008, it was only 44% protective. Even in a bad year for vaccine benefit, vaccination is still our best prevention.

Reducing flu even "moderately" means less flu spreads through our homes, schools and communities. That means less antibiotic use, less time lost from work and fewer hospital stays and deaths, even for people who do get the flu. If you are over 65, it is still hard to say whether the high-dose vaccine might give you an advantage over the regular flu shot. For now, either vaccine is an acceptable choice.

Symptoms that suggest flu are:

• High fever
• Muscle aches
• Cough
• Headache
• (Sometimes) a drippy nose

If you get typical symptoms and you are older than 65, you can consider using oseltamivir (Tamiflu) or another antiviral drug. The CDC recommends treatment with an antiviral drug for:

• People age 65 or older
• People who have significant long-term (chronic) illness

These drugs shorten how long flu symptoms last, but not by much, and they are expensive. The drugs must be started within 48 hours of when symptoms start. They are not as likely to help if you don't start with a very high fever. About one in every six people who take Tamiflu has a side effect of vomiting. It is reasonable to take this drug if you get the flu, but it is reasonable to go without it, too.

What Can I Expect Looking to the Future?

The effectiveness of the high-dose flu vaccine is being studied. Results may be known by fall 2014.

Scientists from the World Health Organization plan and adjust the flu vaccine each year. They represent 112 centers in 83 countries. After tracking flu infections around the world, they have a sense for which strains have caused the most widespread and severe flu infections during the year. Every February, they issue a report. Vaccine makers use the report to develop, produce and distribute the next season's vaccine.

In most years, the flu vaccine targets three strains of flu. It is almost certain that next year's shot will include the flu strain that caused most of this year's trouble. And I hope that it will be more effective against that nasty flu.