# 5318
Although we first heard of encouraging results from Baxter International’s phase III trial of their cell-based vaccine nearly a year ago (see Baxter presents results from Phase III study of Preflucel), today we’ve a study that appears in The Lancet providing us with additional details.
The double-blind, placebo-controlled trial was conducted during the 2008-2009 flu season at 36 locations across the USA. Healthy adults (aged 18—49 years) were randomly assigned to either receive one injection of a placebo or a Vero-cell-culture-derived influenza vaccine.
Overall protective efficacy for antigenically matched influenza infection was determined to be 78.5%, which is comparable to what is traditionally expected from egg-based flu vaccines.
The Lancet, Early Online Publication, 16 February 2011
doi:10.1016/S0140-6736(10)62228-3
Dr P Noel Barrett PhD Gregory Berezuk MS, Sandor Fritsch PhD, Gerald Aichinger MD, Mary Kate Hart PhD , Wael El-Amin MD, Otfried Kistner PhD , Hartmut J Ehrlich MD
(EXCERPTS)
Findings
The vaccine was well tolerated with no treatment-related serious adverse events. Adverse events were mainly mild and transient. An HI titre of at least 1:15 provided a reliable correlate of cell-culture-derived influenza vaccine-induced protection; no additional benefit was noted with titres greater than 1:30.
Interpretation
The data indicate that existing correlates of protection afforded with egg-derived seasonal influenza vaccines also apply to this vaccine.
Details on how this trial was conducted are available at clinicaltrials.gov identifier NCT00566345. A few excerpts follow:
The primary purpose of this study is to demonstrate the efficacy of an investigational Vero-cell derived influenza vaccine to prevent infection in an adult population with an influenza virus that is antigenically similar to one of the three strains in the vaccine.
All subjects will be randomized to receive a single 0.5 ml intramuscular injection from one of three lots of seasonal Vero-cell derived influenza vaccine or saline placebo. Subjects will be monitored for 180 days following vaccination for occurrence of adverse events. For determining antibody response, subjects will have one blood draw before and one blood draw 21 days after vaccination.
Preflucel, an inactivated split-virus vaccine, is only currently licensed for use in Austria and Czech Republic for the 2010 to 2011 influenza season. Baxter obviously hopes that additional countries will look favorably on these trial results.
Cell-based vaccines are being pursued because they may be used by people with egg-allergies, may be quickly produced, and are not dependent upon having the ready supply of hundreds of millions of eggs that are required for traditional influenza vaccine production.
The CDC, on the Flu.gov website, describes the process this way:
The new approach would use mammalian cells (kidney cells are often used) to grow the influenza viruses. Cell-based vaccine production could more easily meet "surge capacity needs" because cells could be frozen and stored in advance of an epidemic or developed rapidly in response to an epidemic. Cell-based vaccine production dramatically reduces the possibility for contamination and promises to be more reliable, flexible, and expandable than egg-based methods.
In place of eggs, cell-based vaccine production utilizes laboratory-grown cell lines that are capable of hosting a growing virus. The virus is injected into the cells where it multiplies. The cells' outer walls are removed, harvested, purified, and inactivated. A vaccine can be produced in a matter of weeks. Polio vaccine is currently produced using the cell-based method.
While both methods could produce an equally effective vaccine, egg-based production is physically limited by the availability of specialized eggs and alone may not be able to meet the accelerated demands of a global influenza pandemic. Cell-based vaccines offer the potential to increase production surge capacity and save lives.
The United States government has spent in excess of $1 Billion dollars over the past few years to accelerate the development and production of new influenza vaccine technologies.
It is well recognized that should another, more virulent pandemic erupt, our current vaccine manufacturing capacity would be woefully inadequate.
