Ever since 1774, when Benjamin Jesty vaccinated his wife with cowpox to protect her from smallpox, vaccines have been at the front lines of our battles against infectious diseases. Now could be their heyday, with some accusations about vaccine safety finally proven false, and more vaccines being developed and even given to older and older patients.
Martha Folmsbee, Ph.D., staff scientist in the scientific and laboratory services department of Pall, will be among the speakers at IBC’s “Vaccine Production Summit” in Boston in June. She will be discussing how filters behave differently under different conditions, so that although filters are tested by their manufacturers, those tests may not be directly relevant if manufacturing conditions differ from test conditions.
According to Dr. Folmsbee, “no filters are absolute for every possible solution,” rather, a specific filter must be chosen for each application. In addition, filter ability and retention can be inversely proportional, so a happy balance must be found. Manufacturers often opt for filtration products that can filter their solutions more quickly, but they need to be aware that by doing so they might be compromising sterility in some cases.
In terms of vaccine production, Dr. Folmsbee warns that adjuvants, often oils, surfactants, and liposomes, can decrease the surface tension of a solution. This lower surface tension can diminish the bacterial retention of any given filter. Adjuvants can also clog filter pores, further reducing their bacterial retention. Some adjuvants—like aluminum salts, some liposomes, and microparticles—may be larger than some bacteria, making filtration of the final solution an ineffective method of terminal sterilization. In such cases each component must be filtered or otherwise purified further upstream in the process, and then the components can be combined aseptically.