Monday, February 28, 2011

FDA Panel Keeps Same Formulation for 2011-12 Influenza Vaccine

From Medscape Medical News

Neil Osterweil

February 25, 2011 — Meet the new influenza vaccine: it's the same as the old one. The trivalent vaccine for the 2011-2012 influenza season in the Northern Hemisphere will probably be essentially a clone of the current season’s vaccine, ruled members of the Vaccine and Related Biologic Products Advisory Committee (VRBPAC) to the US Food and Drug Administration today.

In 3 separate votes, the committee elected to retain the current formulation of the vaccine, containing the following components:

* Influenza A (H1N1) strain A/California/7/2009 (H1N1)-like virus (the pandemic 2009 strain that was distributed in a monovalent vaccine in the United States in 2009);
* Influenza A (H3N2) strain A/Perth/16/2009 (H3N2)-like virus; and
* Influenza B/Brisbane 60/2008-like virus (R/Victoria lineage; this will be third season in which this strain of influenza B has been included in the trivalent vaccine)

The strains are the same as those recommended by the World Health Organization earlier this week.

After considering the best possible information from worldwide surveillance, the committee chose the strains most likely to provide broad coverage of the population at large, but some committee members confessed to being uneasy about the choice.

"In addition to the sleepless night last night worrying about [influenza] B, I’m going to have another one tonight" said temporary voting member Pamela McInnes, DDS, MSc, director of the Division of Extramural Research at the National Institute of Dental and Craniofacial Research in Bethesda, Maryland.

"We make the decision we do with the data we have on the table, but I think for the record there is obvious discomfort and concern about this every year," she added.

She said the inclusion of the influenza B/Brisbane 60/2008-like virus for the third consecutive year is of concern because the current birth cohort may be exposed to other emerging strains not covered in the proposed formulation, such as the influenza B/Yamagata/16/88 lineage, which is less well covered by the current vaccine.

She urged investigators to continue working with new isolates and reagents to help develop a rapid response should new influenza B strains become problematic in the near future.

Resistance to Adamantanes

Slightly more than half (54%) of all influenza viruses antigenically characterized at the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, since the beginning of October 2010 are influenza A (H3N2) isolates, 99% of which were the strain included in the current vaccine, reported Lisa Grohskopf, MD, MPH, a captain in the US Public Health Service, who is also in the Influenza Division of the Epidemiology and Prevention Branch of the CDC.

One third of the isolates (33%) were influenza B, of which 94% were of the Victoria lineage, primarily the B/Brisbane/60/2008-like type covered in the current vaccine. The remaining 6% were of the Yamagata lineage.

Of the 85 influenza A (H1N1) viruses tested (13% of all viruses tested), all were of the strain covered in the current vaccine, Dr. Grohskopf said.

There is high-level resistance to adamantanes (amantadine, rimantadine) among circulating influenza A isolates, but the A(H1N1), A(H3N2), and B virus isolates tested remained susceptible to the neuraminidase inhibitors (oseltamivir [Tamiflu] and zanamivir [Relenza]), she said.

Military Data Suggest Coverage Problems

Data from the global laboratory-based influenza surveillance system maintained by the US Department of Defense (DoD) indicate that there is good agreement between the current vaccine components and the circulating influenza strains, reported Kevin Russell, MD, a captain in the US Navy, director of the DoD’s Global Emerging Infectious Surveillance and Response System, and deputy director of the Armed Forces Health Surveillance Center in Silver Spring, Maryland.

But there is also evidence from a study of 132 active-duty military and dependents suggesting that overall vaccine effectiveness in this group was only 59.7% (95% confidence interval, 51.3% - 68.1%), Dr. Russell said.

In addition, evidence from sentinel surveillance studies suggests poor vaccine protection against A/H1 strains, particularly among those who received the live attenuated influenza vaccine (LAIV) compared with the inactivated vaccine (TIV).

An analysis of data from 36 people with influenza-like illness showed an odds ratio of 2.70 for an illness with flu-like symptoms among those vaccinated with LAIV compared with TIV, Dr. Russell said.

Febrile Seizures

Children younger than 2 years who received both influenza vaccine by Sanofi Pasteur (Fluzone) and the new pneumococcal conjugate vaccine by Wyeth (Prevnar 13), had a slightly elevated risk for febrile seizures, reported David Martin, MD, MPH, an electrophysiologist in the Department of Cardiovascular Medicine at the Cleveland Clinic in Ohio.

Data from the Vaccine Adverse Event Reporting System and the Vaccine Safety Datalink system suggested a small risk in children age 12 to 23 months, but not in the larger cohort of children age 6 to 23 months or those older than 23 months, Dr. Martin said.

Vaccine safety investigators will continue with case ascertainment until the end of the current flu season. They will review charts of all cases that received one or both vaccines, Dr. Martin said.

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