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Does the high-dose flu shot protect better than a regular flu shot?

Posted By Anthony Komaroff, M.D. On December 23, 2015 @ In Cold and Flu,Vaccines | Comments Disabled

DEAR DOCTOR K:

I’ve heard that there is a high-dose flu shot. Does it protect better than a regular flu shot? Should I ask my doctor about it?

DEAR READER:

The high-dose flu vaccine, known as Fluzone, is approved for adults ages 65 and older. It may provide better flu protection for older adults than the standard flu vaccine, which is less effective in older adults than in younger adults.

Both the high-dose and standard flu vaccines target three different strains of the flu virus, selected from the most common strains predicted to be circulating that year. In both vaccines, the viruses are inactivated, or killed, so they cannot cause the flu, even in people with weakened immune systems.

Both vaccines can cause mild symptoms of arm pain, redness, muscle aches or low-grade fever. Most people have minimal to no symptoms. But the high-dose vaccine may slightly increase side effects.

The big difference is that the high-dose vaccine contains four times the dose of immune-stimulating antigens as the regular flu shot. This provokes the body to mount a greater immune (antibody) response.

A study published in the New England Journal of Medicine looked at the effectiveness of the high-dose vaccine, compared to the regular flu vaccine, in older adults. Researchers randomly divided nearly 32,000 adults, ages 65 or older, into two groups. One group received standard flu shots. The other group got high-dose flu shots.

Those who got the high-dose shots were 24 percent less likely to develop flu than those who got the standard shots. The researchers estimate that the high-dose flu shot provides seniors with the same level of protection that younger adults receive from the standard flu shot.

An annual flu shot can help older adults avoid flu complications such as pneumonia. The flu shot is even more crucial for older adults who are at higher risk for serious complications because of existing health conditions. Getting the shot each year can help prevent hospitalization or death from flu complications.

The study I discussed earlier does not tell us whether Fluzone reduces serious complications of flu. But it does suggest the higher dose helps the body mount a stronger defense.

One of the problems with any of the types of flu vaccine currently available is that different flu viruses circulate each year. Thus, the vaccine is a little different each year. It takes months to make enough vaccine to be ready for flu season, and that means the vaccine makers need to guess correctly which flu strains will be circulating months in the future. Those guesses are not always perfect.

In recent years, medical research has identified what are called broadly neutralizing antibodies that attack most strains of the flu virus. Many research teams are pursuing ways that these antibodies might be exploited to give better protection against the flu than current, imperfect vaccines.

Though the high-dose flu shot may provide better protection, any flu shot is better than none. For best results, get the shot early in the flu season, which runs from October to May.


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