Gambia pertussis study
GaPs is the largest single study in the project and is being run at the Medical Research Council–funded London School of Tropical Medicine center in Gambia. Beate Kampmann, MD, PhD, of Imperial College London, England, is the project lead. It is due to complete in 2022. GaPs seeks to enroll 600 mother/infant pairs and randomize the mothers to either an acellular pertussis booster in pregnancy or a tetanus toxoid control vaccine. Infants are subsequently randomized to an acellular or whole-cell pertussis schedule of primary immunization. The vaccine doses are being given at 2, 3, and 4 months. The primary endpoint is a serological finding being measured at 9 months of age, when the infant would usually receive yellow fever, measles, and rubella vaccination.
GaPs has a number of pathways. Within each of the four arms generated by the two randomizations, the maternal randomization and the infant randomization, there are five subgroups. They are designed to study time points in subgroups A and B after the first dose in more detail, looking at the innate immune responses using gene expression. It will enable researchers to study adaptive immune responses to T cells and B cells after the second dose of vaccine. By employing a range of subgroups, the team can explore the immune profile using the assays referred to above. Such information should provide new insights into the differences between acellular and whole-cell vaccines.
The AWARE study
AWARE is the sister study to GaPs and looks at the acellular/whole pertussis issue. Because many developed countries, such as the United Kingdom, have established maternal immunization programs, it is not possible to randomize mothers. Consequently, researchers have opted to recruit infants of mothers who have received an acellular vaccine in pregnancy and randomize them to either an acellular schedule of primary immunization or a whole-cell schedule.
The selected vaccine is ComVac5 from Bharat Biotech. This whole-cell vaccine differs from that used in Gambia. An early obstacle for AWARE has been seeking permission to import a non-conventional vaccine into Europe. It has delayed the anticipated end date to 2023. Participating infants will receive a two-dose schedule at 2 and 4 months of age per their randomization; then, both groups will go on to receive an acellular pertussis booster at 12 months. At all time points, the team will sample blood for cells and serum, as well as mucosal fluid from the nose. Because the mucosal surface is where the action is, this approach will likely generate new data around antibody responses.
The MIFI
The Pertussis Maternal Immunization Study in Finland is being run by Jussi Mertsola, of the University of Turku, Finland, and Qiushui He, of the National Public Health Institute, Turku. It is due to complete in late 2021. Where, in the United Kingdom, researchers are unable to randomize mothers because of the current guidelines, researchers in Finland do not have a maternal immunization program to consider. MIFI will randomize 80 mothers, 40 to immunization with acellular pertussis and 40 to a control group. Dr. Kelly stated that whole cell vaccines are not available for use in Finland. Participants will receive a two-dose schedule at 3 and 5 months. Blood samples will then be taken to compare the serological and cellular responses, which will help researchers understand the effects of maternal immunization. In addition, there will be sampling of mucosal fluid using a device that collects a standardized aliquot of fluid.