A new influenza vaccine grown in cultured animal cells rather than eggs is at least as effective as conventional vaccines, a finding that could speed approval of the new way of producing the vaccine, researchers reported Tuesday. If the manufacturing technique is approved, it could improve the ability of vaccine makers to respond to emerging viruses and pandemics. The vaccine for the recent H1N1 influenza pandemic, for example, did not become available until the outbreak had already crested. If manufacturers had been able to use the new production technique, the vaccine could have been produced eight to 10 weeks earlier, when it would have been much more useful.
Flu vaccines have been made in fertilized chicken eggs for more than 50 years because the virus uses protein in egg white to grow and the technology has a long history of safety. But in addition to the process being slow, some people are allergic to eggs, the virus can mutate in the eggs, and microbial contamination can easily occur. Growing the virus in animal cells can minimize most of those problems. The cells are already used to produce most other vaccines, such as those for polio and rabies. The vaccine is produced in Vero cells, which are derived from the kidneys of African green monkeys.
The new vaccine, called Preflucel, was developed by Baxter International and DynPort Vaccine Co. with a grant from the U.S. Department of Health and Human Services, which awarded $1.3 billion to six companies in 2006 to develop the new technology. HHS paid for the new clinical trial as well. A similar study involving a vaccine developed by Novartis reported success in November.
The new study involved 7,250 healthy adults during the 2008-09 influenza season. Half received Preflucel and half a placebo. Dr. P. Noel Barrett of Baxter and his colleagues reported online in the journal Lancet that the vaccine was 78.5% effective in preventing influenza. Conventional vaccine is typically about 73% effective, they said. The vaccine was well-tolerated with no treatment-related side effects.
The use of vaccines grown in a tissue culture substrate could shorten production time by as much as 10 weeks, "which might be crucial in a pandemic alert," wrote microbiologist W. Paul Glezen in an editorial accompanying the report. It could also allow health authorities to wait longer before choosing which strains will go into each season's vaccines, thus ensuring a better match with the circulating strains.
Preflucel is already approved for sale in Austria and the Czech Republic and is expected to win approval in most of Europe later this spring. The company is in talks with the Food and Drug Administration about whether the new results are sufficient to win approval in this country, Barrett said.