February 21, 2014
News Review From Harvard Medical School -- CDC: Flu Hitting Younger Adults Hard
Young and middle-aged adults are getting flu at higher rates than usual, U.S. health officials say. About 61% of those who have had a hospital stay because of flu this season were adults age 64 and younger, the Centers for Disease Control and Prevention (CDC) said. In the previous 3 years, 35% of those hospitalized were in this age group. People 25 through 64 years old also have accounted for 60% of deaths this season, the CDC said. That's three times the percentage of other recent seasons. The CDC noted that younger adults are less likely to get flu shots than older adults. Most of the serious illness in this group has been caused by the H1N1 flu virus. H1N1 is the dominant U.S. strain this year for the first time since 2009, when it caused a worldwide pandemic, the CDC said. H1N1 causes serious illness in young adults more often than other strains of influenza. Flu shots do help, health officials say. And it's not too late to get shots, especially in some areas. The CDC said these include the West and Northeast, where flu activity picked up in January. HealthDay News wrote about the CDC report February 20.
By Mary Pickett, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
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, I know. The Centers for Disease Control and Prevention (CDC) just released estimates about how well this year's flu shot is doing its job. This year the flu vaccine is 61%, 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.
Truly this is not a bad result. Or, you might say, it is "nothing to sneeze at." How does 61% compare? It is about as effective as last year's vaccine. In our best years, the flu shot protects against 70% to 90% of circulating flu virus infections. Six years ago, in 2007-2008, it was only 44% protective.
But even when it isn't perfect, vaccination is still our best prevention.
One specific flu virus, influenza A (H1N1), accounted for 98% of the flu cases that were detected this year. As a surprise, flu has hit young and middle-aged people particularly hard. People ages 18 through 64 made up 61% of all people who were hospitalized with flu -- almost double what is usual. More influenza deaths than usual also occurred in this younger age group.
The CDC's estimate of effectiveness for this year's flu vaccine is based on 2,319 people who had severe enough cough and cold symptoms to see a doctor. All of the patients had nasal swab tests to check for influenza (flu). In all, 29% of people who tested positive for flu reported that they had the flu vaccine earlier in the year. About 50% of those who tested negative for flu said they had received the vaccine.
Researchers adjusted these numbers to account for things besides vaccines (such as age and health) that affect people's risk of infections. They found that the vaccine was 61% effective.
What Changes Can I Make Now?
A flu shot is strongly recommended for all people older than 6 months. It's not too late to get one.
Reducing flu, even "moderately," means that less flu virus spreads through our homes, schools and communities. That means less time lost from work and fewer hospital stays and deaths, even for people who do get the flu.
Symptoms that suggest flu are:
- High fever
- Muscle aches
- (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 given 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 person out of every six taking 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?
When the CDC says 61% effective, which flu vaccine is the CDC talking about? All of them.
This year, many people might have not realized that their pharmacy or clinic had several to choose from. They included:
- Trivalent or quadrivalent (targeting either three or four flu viruses)
- High-dose or standard dose
- Nasal spray (for people under age 50) or injectable
- Shots that go just under the skin or into a muscle
- Vaccine that was grown in egg culture or egg-free
When completing the initial effectiveness report, the CDC report lumps all of these vaccine types together.
The biggest unanswered question is whether the high-dose vaccine is more effective in older people than the standard dose. The high-dose version was developed for people over age 65. It has been available for 2 years.
Early studies show that older adults had had 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. This is being studied now. Results may be known by fall 2014. 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. For now, either vaccine is acceptable.