Baxter Claims Successful Trial Of Cell-Based H5N1 Vaccine

First clinical trial of an H5N1 avian influenza vaccine has given favorable results so far. The vaccine contains dead H5N1 virus grown in cell culture which may enhance immune response against the virus and curtail the production time.

The vaccine formation involves a bit of risk due to the virus cell culture but reports have shown satisfactory results. The vaccine manufacturer, Baxter Bioscience, confirmed immune responses against the virus in most of the volunteers. The vaccine has reportedly caused fewer side effects. Vaccine formula without immune boosting substance has generated good results.

Earlier tested vaccines for H5N1 were made by conventional method which requires growing a genetically modified virus in chicken eggs. This process takes several months. But the new formula is developed as a Vero cell culture, which is fast and flexible.

Baxter has used a whole & inactive, "wild-type" H5N1 virus in the vaccine as a substitute for genetically modified and weak virus. There are evidences that whole-virus vaccines against flu outbreaks can be more successful than others.

Huge amount of a wild-type H5N1 virus is actually a threat. If virus escapes, it may lead to flu outbreak. Baxter grew the virus in a high-security (biosafety level 3) unit. Made in in Bohumil, Czech Republic, the vaccine is named Celvapan.

In a recent news report, Baxter spokesman said "Baxter's Vero cell manufacturing process is more rapid due to its ability to use a 'native' virus that does not need to be modified to allow growth in chicken eggs, therefore accelerating vaccine production".

The vaccine uses a clade 1 strain of H5N1 virus. Total 284 volunteers, aged 18-45 years were administered this vaccine, twice, with a gap of 21 days with and without adjuvant. The trials were conducted in Austria and Singapore.

Hartmut J. Ehrlich, MD, and Noel Barrett, from Baxter led the research. The team evaluated immune responses by determining neutralizing antibodies, defining seroconversion with a minimum fourfold augment in antibody titer, 21 days after the first and second doses. The higher rates of seroconversion were found in those who received vaccine without adjuvant. Also,more immune response was studied in this group.

The formula without an adjuvant produced high cross-reactivity rates against clade 3 virus. Few common side effects were headache, fever and pain depending on the formulation.