Harvard Health Letters
If you got a flu shot last year and it didn’t work, don’t reject vaccination.
During last year’s battle of The People vs. Influenza, the virus gained the upper hand. Early in the 2014-15 flu season, a new strain of the virus emerged against which the existing vaccine offered virtually no protection. Hospitalizations for flu in older adults spiked to the highest level in a decade.
Last year’s severe flu season is a reminder that the effectiveness of vaccination varies from year to year. If you got the shot but fell ill with flu anyway, don’t let that experience put you off of vaccination. It always reduces the risk of illness — just more so in some seasons than others.
“If you get vaccinated, you are less likely to get infected and also less likely to progress to a severe health complication,” says Edward Goldstein, a senior research scientist at Harvard’s T.H. Chan School of Public Health.
The flu can hit harder in people 65 and older because, as a group, they have less ability to withstand the stress of an illness.
“Even if they don’t have some other chronic health condition, if the flu is severe enough, it can make older adults seriously ill,” says Dr. Jatin Dave, a geriatrician at Harvard-affiliated Brigham and Women’s Hospital, Boston. “In frail older adults with multiple chronic conditions, influenza can be fatal.”
What happened last year
Every year, the World Health Organization tracks flu activity across the globe and predicts which viral strains are likely to dominate in the following season. In North America, the season runs from October to May but usually peaks in February. Vaccines contain fragments of three or four strains, which cause the immune system to make antibodies to the virus and protect you from infection.
But early in the 2014-15 season in the U.S., the new viral strain emerged and began to infect a lot of people. As a result, at least one in 300 people 65 and older was hospitalized with severe complications stemming from influenza infection, such as dehydration and pneumonia.
Vaccine effectiveness depends on how closely the strains included in the flu shot match the ones that infect most people. Because the vaccine did not include the new strain, its overall effectiveness was only 19 percent. That means only about one in five people vaccinated had sufficient immunity to fight off the flu. In a good year, the effectiveness can be 60 percent or greater.
The likely benefit of flu vaccination also depends in part on the age and health of the person being vaccinated. In general, the younger and healthier you are, the more protection you get.
Benefits of vaccination
Mismatches don’t happen every season. If vaccination did nothing for you last year, that doesn’t mean it won’t work this year. The main benefit of vaccination is a lower chance of having to endure a week of fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills, and fatigue. By being vaccinated, you are also less likely to infect someone else.
The stakes are higher for people with certain health conditions that put them at greater risk for severe flu complications — mostly pneumonia. In such cases, annual vaccination is strongly recommended.
The CDC and other medical organizations recommend that anyone at higher risk of severe flu complications get treated promptly with an antiviral medication when they start to feel flu symptoms. Starting on drugs early suppresses the virus before it has a chance to trigger more serious health problems. The two available are oseltamivir (Tamiflu), taken as a pill, and zanamivir (Relenza), which is inhaled. These drugs help prevent hospitalization for such complications as pneumonia.
According to the CDC, these symptoms indicate a dangerous flu infection that requires immediate medical attention:
–being so sick you can’t keep food or fluids down
–difficulty breathing or shortness of breath
–pain or pressure in the chest or abdomen
–severe or persistent vomiting
–flu-like symptoms that improve but then return with fever and worse cough
What you need to know
Who: The CDC recommends annual vaccination for everyone 6 months and older to prevent influenza infections. Certain health conditions raise the risk of dangerous flu complications. The most common ones are lung disease, heart disease, dementia, diabetes, and kidney or liver disease. Vaccination for high-risk individuals is highly recommended.
When: Get vaccinated as early as you can, but understand that during the two to four weeks it takes to build immunity, you could still con-tract the flu.
What: A variety of flu shots are available. Vaccines are usually injected into the muscle, although a version is available that can be injected under the skin. There’s also an inhalable (nasal) vaccine. A new, high-dose version of the flu vaccine, called Fluzone, is intended to help older adults mount a stronger defense against the flu, although it may cause more side effects.
Side effects: The most common side effect of vaccination is pain at the injection site; other possibilities are a low fever or nausea and vomiting. – Harvard Men’s Health Watch