Quadrivalent Influenza Vaccine

Our annual article on this year’s influenza vaccine in the September 16, 2013 issue of The Medical Letter reported that new quadrivalent vaccines offer additional protection against influenza B viruses. An article published in the December 26, 2013 issue of The New England Journal of Medicine and an accompanying editorial offer some interesting additional information on this subject.

The article by VK Jain et al reported the results of a clinical trial of the new inactivated quadrivalent vaccine in nearly 5000 children 3-8 years old, using a hepatitis A vaccine as a control. The quadrivalent vaccine was more than 70% effective in preventing moderate-to-severe influenza, which is about the same efficacy rate as has been reported with trivalent influenza vaccine. The trial could not demonstrate any advantage from the inclusion of the extra B antigen because only 2 cases of influenza related to that antigen were reported, both in the control group. The quadrivalent vaccine was immunogenic against all 4 strains and was not associated with any increase in adverse effects.

The editorial by LR Baden explains the rationale for adding a second B antigen to the vaccine. Traditional trivalent influenza vaccine contains A/H1N1, A/H3N2 and a single B antigen. But for many years there have been 2 main influenza B lineages in circulation, and the inclusion of one or the other in a trivalent vaccine has resulted in a mismatch 50% of the time. The addition of a second B antigen should offer some degree of protection against influenza B illness every year. Influenza B causes less influenza illness than influenza A, but a B antigen mismatch still can have serious consequences. Baden quotes an estimate from the 2007-2008 influenza season, in which a mismatch occurred, that inclusion of the second B antigen in that year’s vaccine could have prevented, per 100,000 population, 440 influenza-associated illnesses, 4.13 hospitalizations, and 0.22 deaths.

Does that make the quadrivalent vaccine worthwhile? Well, if it truly is just as efficacious as the trivalent vaccines in preventing illness, hospitalizations, and death from any strain of influenza, without any additional side effects, and the best we can do in identifying the circulating B antigen(s) is guess, I suppose so. But I might want to wait a year or two to find out a little more about all of that.

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