Q. Should two flu shots protect me better than one?
A. Booster doses can make influenza vaccine more effective, but the benefit is limited to any specific groups.
Children are a group who can benefit from receiving two doses of influenza vaccine during the same flu season. In a multistate study, increased vaccine efficiency increases almost twice in children 6 months to 8 years. The benefit was greatest among infants who received their first flu vaccinations and were still apparent in subsequent flu season. Other studies have given similar results.
Pandemic flu, a worldwide epidemic caused by genetic variations of the influenza virus, is another situation in which booster dosing may be worth, because our immune system is not primed to mount a response to the new virus. But vaccination strategies are complex and must be guided by state health care agencies. Just taking two doses of the current vaccine will not be protected.
Finally, organ transplant recipients can benefit from booster doses studies have shown. Unfortunately, the benefit does not seem to extend to other groups that may have compromised immunity, such as those with inflammatory bowel disease, leukemia, HIV or renal failure.
Although men and women 65 years of age and older are also at high risk from flu complications, it does not seem to give rise to benefits in this age group. In two studies of patients in the 70’s, the second dose of vaccine failed to increase antibody levels against flu. However, elderly men and women receive extra protection from a single shot of high-dose flu vaccine.
Outside these groups, where safety and efficacy have been shown, one should not take a booster dose of influenza vaccine on the theory that at worst it would be harmless. Booster doses are associated with increased risk of side effects, including fever, rash, shortness or breath and injection site pain.
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