Will poor match hurt vaccine efforts?
Will poor match hurt vaccine efforts?
CDC: Overall effectiveness was 44%
This past winter, influenza vaccine expert Gregory Poland, MD, director of the Mayo Vaccine Research Group at the Mayo Clinic in Rochester, MN, got the flu. Yes, he had the flu vaccine. But this year, the vaccine was not a good match with the prevailing strains.
In fact, the Centers for Disease Control and Prevention in Atlanta reported that two of the three strains in the 2007-2008 vaccine were "suboptimally matched," and that the overall effectiveness of the vaccine was 44%.
Will this season's poor vaccine match affect future health care worker influenza vaccination? What do you tell health care workers about the vaccine if they use the poor match as an excuse to remain unvaccinated?
"It's imperfect, but it's the best that we have," says Poland. "It's significantly effective when you look across years and across populations."
The effectiveness of the vaccine was tested among patients with influenza who came to Marshfield (WI) Clinic facilities between Jan. 21 and Feb. 8. The influenza B strains detected were antigenically distinct from the B strain included in the vaccine. Seven of nine influenza A viruses had drifted from the A strain used in the vaccine. Two influenza A (H3N2) viruses were similar to the vaccine strain.
Just 19% of the patients who tested positive for influenza had been vaccinated.
"In this analysis, preliminary vaccine effectiveness results indicated that, despite the antigenic differences between vaccine and circulating H3N2 strains, the effectiveness of vaccine in preventing medically attended respiratory illnesses from influenza A infections was 58%," the researchers concluded." In contrast, no vaccine effectiveness could be demonstrated against influenza B."1
While in some years, the flu vaccine has been even less effective than this year's vaccine, in general the match is significantly better, says Dan Jernigan, MD, MPH, deputy director of CDC's influenza division. "In the last 20 seasons, 16 have had good matches and there have been four that were less than optimal matches," he said in a press briefing.
Bruce Cunha, RN, MS, COHN-S, manager of employee health and safety at the Marshfield Clinic, is already anticipating the comments he will get during the next vaccination season. His spin: The vaccine worked well for the A strain that was a better match.
"We would have had a lot more hospitalizations and fatalities. That's the message we have to get out," he says. "It still does give you protection."
That also was the message from CDC. "The measurable benefit demonstrated in this study supports existing public health practice of continuing to recommend influenza vaccination even when there is indication of a suboptimal match between the vaccine viruses in circulating influenza viruses," Jernigan said in the briefing.
Meanwhile, Marshfield Clinic emphasized its respiratory etiquette ("Cover your cough") program, masking patients and employees with respiratory symptoms, Cunha says.
While it is discouraging to have a vaccine that is less than optimally effective, Poland notes that employees may realize how important it is to prevent the disease with both vaccination and infection control practices.
Poland said he suffered from a "bacterial superinfection" after getting the flu and took two sick days his first in the past 20 years. "It impresses it upon you in a more personal way," says Poland. He imagines how severe it could be for an elderly person with other health problems. "I understand why people die of it," he says.
Reference
1. Belongia E, Kieke B, Coleman L, et al. Interim within-season estimate of the effectiveness of trivalent inactivated influenza vaccine Marshfield, Wisconsin, 2007-08 Influenza Season. MMWR 2008; 57:393-398.
This past winter, influenza vaccine expert Gregory Poland, MD, director of the Mayo Vaccine Research Group at the Mayo Clinic in Rochester, MN, got the flu. Yes, he had the flu vaccine. But this year, the vaccine was not a good match with the prevailing strains.Subscribe Now for Access
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