A Trial Comparing Two Pertussis-containing Vaccines in Pregnancy and Vaccine Responses in UK Mothers and Their Infants

Due to an unexpectedly high number of infant deaths from whooping cough in 2012, the Department of Health acted to protect newborns between birth and completion of primary immunisations, the period with greatest risk of disease. Vaccination of pregnant women with whooping cough vaccine in the third trimester of pregnancy was instigated nationally, so that antibodies produced by the Mum would cross the placenta to the unborn child, giving them passive protection at the most vulnerable time. This antibody transfer has been known for some time but has not been compared between the two whooping cough vaccines being used in pregnancy. Any effect the raised antibody might have on infant responses to the vaccines given in the first few months of life has also not been measured. This is particularly important as the infant immunisations include some of the same components as the whooping cough vaccines, which include diphtheria, tetanus and polio. Previous studies have shown that high levels of antibody prior to vaccination may affect subsequent antibody responses. It is therefore important to assess whether administration of the whooping cough vaccine in pregnancy adversely affects the protection afforded by the infant vaccines, particularly to those which are similar, namely tetanus and diphtheria as well as meningitis C and Hib vaccines which include diptheria and tetanus components in their structures. This study will assess immune responses of mothers and their babies (\~200 pairs) to their vaccinations and will allow the comparison of two whooping cough vaccines being used in pregnancy. This will be done by taking small amounts of blood, which is the only way to measure antibody levels (the proxy of the immune response), before and after the vaccinations. A group of unvaccinated women and their babies (50 pairs) will also be recruited to allow comparison of their immune responses.