| Sandra Adamson Fryhofer, MD
Adjunct Clinical Associate Professor of Medicine, Emory University School of Medicine, Atlanta, Georgia; Past President, American College of Physicians
Next Year's Flu Vaccine: What to Know Before You Order
This issue of Staying Well focuses on influenza vaccination, an annual public health initiative, and reviews new influenza vaccine formulations available for next season.
On February 20-21, 2013, I attended the Advisory Committee on Immunization Practices (ACIP) meeting as the liaison representative for the American Medical Association. (For full disclosure, I am also a member of the Influenza ACIP Working Groups for the influenza, human papillomavirus, and pneumococcal vaccines.) Day 2 of the meeting could be described as a "fluathon."
Highlights from this discussion may help you when placing flu vaccine orders for next year. A recent report on influenza vaccine efficacy in Morbidity and Mortality Weekly Report (MMWR)also warrants further comment.
Editor's Note: Since the publication of this commentary, the CDC has provided interim recommendations on the vaccines that will be available for the next flu season.
A Look Back
The 2012-2013 influenza season started about 4 weeks earlier than usual. Flu activity spiking in late November led to an increased consumer demand for vaccine in late December and early January compared with previous years. Fortunately, vaccine shortage has not been a problem for this season. The final influenza vaccine dose count produced for the US market for the 2012-2013 season is 145 million. Of that, 134.8 million had been distributed by February 8, 2013.
The 2012-2013 flu season has been characterized as moderately severe, with high hospitalization rates for seniors. The predominant culprit was influenza A (H2N2); however, B viruses also caused infection. Current trivalent influenza vaccine covers 2 A strains and 1 B strain, which, this year, were good matches for the circulating strains. That has not always been the case.
Fortunately, resistance to antiviral medications has not been an issue this season. All of the influenza B and influenza A H3N2 viruses tested were susceptible to both oseltamivir and zanamivir. Oseltamivir resistance was observed in only 0.9% of the circulating 2009 H1N1 viruses. This strain was included in the 2012-2013 vaccine.
Influenza Vaccine Effectiveness Revealed: Half Empty or Half Full?
Estimates of mid-season vaccine effectiveness were presented to ACIP and then published in MMWR on February 22, 2013. The overall combined adjusted effectiveness of the vaccine against influenza A and B was 56%: 47% protection against influenza A (H3N2), and 67% protection against B viruses. Vaccination cut outpatient medical visits due to influenza A (H3N2) in half for the under-65 age group, and cut those due to influenza B by 67% for all ages.
Media headlines highlighted poor protection among elderly persons. The breakdown in protection comes from influenza A (H3N2) viruses in those older than 65 years. For the senior set, vaccine effectiveness estimates were a dismal (and nonsignificant) 9% protection against influenza A (H3N2). This reiterates the importance of vaccinating everyone over 6 months old of age -- not only for their sake, but for that of older family members and friends. If children and younger adults don't get vaccinated, they are more likely to get the flu and could pass it on to seniors, with deadly consequences.
Why seniors did not mount a significant immune response to the influenza A (H3N2) component of this season's vaccine is not entirely clear. Immunosenescence has a role. As we age, our immune system also ages and does not work as well. This phenomenon was the impetus for the high-dose flu shot for seniors, a way to boost immune response. This season's nonsignificant vaccine effectiveness against influenza A (H3N2) for seniors also demonstrates the need for better and more effective vaccines (especially for this older age group) and the importance of antiviral medications in symptomatic individuals, regardless of vaccination status.
Medscape Internal Medicine © 2013 WebMD, LLC
Cite this: It's Shopping Season Now for Next Year's Vaccine - Medscape - Apr 08, 2013.