Quadrivalent flu vaccine discussed

The Vaccines and Related Biological Products Advisory Committee discussed potential risks and benefits of adding coverage for a second influenza B strain.

Since 2000, two influenza B lineages — Victoria and Yamagata — have been co-circulating worldwide, prompting health care officials to consider developing a quadrivalent influenza vaccine that would extend protection against both. But questions such as how to implement such a vaccine, and the actual public health contribution additional influenza B coverage would make continue to be debated.

“Protection after vaccination with one lineage against the other is limited and some degree of mismatch occurs each year,” Carrie Reed, DSc, MPH, an epidemiologist in the CDC’s influenza surveillance branch, said during the Vaccines and Related Biological Products Advisory Committee (VRBPAC) meeting.

Using data from the past 10 influenza seasons, Reed, along with Anthony Fiore, MD, MPH, CDC liaison to the Advisory Committee on Immunization Practices influenza working group, developed a model to project the risks and benefits of a quadrivalent influenza vaccine.

The researchers predicted that replacing the current trivalent vaccine with a quadrivalent vaccine would have resulted in an estimated 1,090,514 fewer cases, 7,488 fewer hospitalizations and 321 fewer deaths associated with influenza.

Vaccine protection would vary by season depending on vaccine supply. If current manufacturing trends continue and excess vaccine supplies remain available, the reduction in available doses that a quadrivalent vaccine would create would not have a significant effect on actual vaccine protection rates, Reed said.

Fiore emphasized that additional information would be necessary before a favorable quadrivalent vaccine recommendation could be issued. More data on clinical safety, immunogenicity and efficacy; a better understanding of manufacturing issues and constraints; development of a regulatory path and a thorough economic assessment would be needed. – by Nicole Blazek

It is important to clarify that the numbers of cases, hospitalizations and deaths quoted are cumulated over a 10-year period, had the trivalent vaccine actually been a quadrivalent vaccine. In some years, a quadrivalent vaccine was estimated to save some lives; in other years, the quadrivalent vaccine might actually have cost some lives. It was an interesting model, and I commend the investigators from CDC for developing it. I'm not sure, however, how useful it will be in finally making a decision about this.

Discussions about putting two influenza B components in the vaccine have been going on since the Yamagata and Victoria strains began co-circulating some 15 to 20 years ago. Prediction of which of the two strains will predominate in the following season are mostly guesswork, and the committee's guess for the current season was wrong. In the past, production was limited, and the inclusion of another vaccine component would have necessitated either reducing the dose of each antigen, or reducing the total number of doses of vaccine produced. Today, however, production capability has been substantially increased, and the manufacturers now are both willing and able to produce a four-component vaccine with 15 mcg of each component.

The primary use of a quadrivalent vaccine would likely be in the pediatric market; I believe a quadrivalent vaccine has little to offer for adults and those over 65 years of age.

– Theodore Eickhoff, MD

Infectious Disease News Chief Medical Editor

For more information:

FDA Center for Biologics Evaluation and Research Vaccines and Related Biological Products Advisory Committee Meeting; Feb. 18-19, 2009; Washington.