High-Dose Flu Vaccine (HDV)
- What is high-dose flu vaccine (HDV)?
- Why was the HDV for seniors developed?
- Is there evidence that the HDV provides better immunity than the SDV against the flu in seniors?
- Is the HDV safe?
- I am a senior. Should I get the new HDV?
What is high-dose flu vaccine (HDV)?
In 2009, the U.S. Food and Drug Administration (FDA) approved a high-dose influenza vaccine (HDV) for use in persons 65 years of age and older.
The brand name of the vaccine is Fluzone High-Dose and it is manufactured by Sanofi-Pasteur. The vaccine is given as a single injection in the arm like the traditional flu shot, but it contains four times the antigen dose per flu strain compared to the standard-dose vaccine (SDV). The current HDV is “trivalent,” meaning it contains antigens from only 3 strains of flu virus (2 A strains and 1 B strain). In contrast, as of last season, PAMF has offered a SDV that contains 4 flu strains (2 A strains and 2 B strains) and is thus termed “quadrivalent.” In the future, the HDV may be quadrivalent as well, but not in the current season.
HDV will be available to patients 65 and older in provider offices at PAMF, in the weekend Flu Express Clinics, and in weekday flu clinics for the 2014-2015 flu vaccination season – see the PAMF flu website for dates and locations of flu clinics.
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Why was the HDV for seniors developed?
Persons 65 and older typically have the highest rates of hospitalization and death from the flu. However, the protection provided by SDV is not as strong as in younger patients. Part of the problem may be that antibody levels are not high enough with SDV. Researchers are exploring a variety of ways to boost the immune response in seniors, and increasing antibody levels with HDV is one of them.
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Is there evidence that the HDV provides better immunity than the SDV against the flu in seniors?
A study done in seniors during the 2006-2007 flu season comparing HDV and SDV showed higher antibody levels for the two A flu strains with HDV but no difference for the B strain (Journal of Infectious Diseases, 2009; 200:172-180). While encouraging, the study did not address whether HDV was more effective in actually preventing the flu. In contrast, a more recent study examined the effectiveness of HDV in preventing the flu (New England Journal of Medicine, 2014; 371:635-45). It showed HDV to be 24% more effective than SDV in preventing laboratory-confirmed flu in persons 65 or older. However, the absolute difference in flu infection between the two groups was small (1.4% with HDV vs. 1.9% with SDV) thus making the benefit of HDV a relatively modest one. The study did not examine the effect of HDV on preventing serious complications of flu like hospitalization and death. Both studies were randomized, controlled trials and were industry-funded.
Subsequently, two cohort studies examined the effect of HDV vs. SDV in preventing flu-related hospitalization in seniors, a very important outcome. The first found a 22% benefit of HDV over SDV (Lancet Infectious Diseases 2015; 15:293-300) while the second suggested this benefit might be limited to patients 85 years of age or older (Clinical Infectious Diseases 2015; 61:171- 6).
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Is the HDV safe?
Minor adverse effects may be slightly more common with HDV than SDV. For example, pain at the injection site and fever above 100.4 degrees were both more common with HDV (36 versus 24 percent, and 1.1 versus 0.3 percent, respectively). A follow up study of adverse effects showed no strong trend in problems with HDV although gastrointestinal symptoms seemed to be more common with HDV. (Post licensure safety surveillance for high-dose trivalent inactivated vaccine in the Vaccine Adverse Event Reporting System, 1 July-31 December 2010. Clinical Infectious Diseases 2012; 54:1608-14). There does not appear to be a difference in major adverse effects between HDV and SDV.
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I am a senior. Should I get the new HDV?
The Advisory Committee on Immunization Practices for the Centers for Diseases Control and Prevention has not expressed a preference for either the HDV or the SDV for those 65 or older. Both are considered good vaccines for seniors. However, HDV appears to have a modest edge over SDV in preventing flu and possibly hospitalization as well in this age group. Because of this, a number of PAMF physicians prefer HDV over SDV for their senior patients. Meanwhile, HDV comes with a slightly greater incidence of minor side effects but no increase in major side effects. The current HDV, which is trivalent, has not been compared with quadrivalent SDV.
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