MICA:The immunogenicity of combined pertussis-containing vaccine (Tdap) for HIV-infected pregnant women and their newborns-A Randomized Clinical Trial

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This study will work out whether vaccinating pregnant women in Uganda with a pertussis (whooping cough) vaccine might be useful to help prevent babies in Uganda from becoming ill or dying with whooping cough. Babies in countries like Uganda are usually vaccinated against pertussis at 10, 14 and 16 weeks of age, and until these injections are completed, babies are at risk of getting pertussis infection and becoming unwell or dying. Until a baby is fully vaccinated, they rely on their own immature blood cells and also protection passed across the placenta in the form of antibodies from their mother during pregnancy. One way that we could protect these vulnerable babies is by vaccinating pregnant women with a whooping cough vaccine called Tdap, to increase the antibody levels in the mother's blood so that more protection can pass across the placenta into the baby. This is already being done in countries like the U.S and the U.K, and we know it is effective in reducing the number of babies becoming sick with whooping cough. The WHO has recommended that Tdap be offered to pregnant women around the world. However, there are no studies looking at whether giving the vaccine in countries like Uganda, where there is a high burden of HIV disease, will work in the same way. We know that vaccinating a pregnant woman with pertussis vaccine may reduce a baby's response to their own vaccines, which could leave the baby unprotected. However, babies in Uganda receive a different type of pertussis vaccine (wP) to the one used for babies in the U.K/U.S. This vaccine is thought to be more effective in countries where there is a lot of pertussis. We do not know if the same reduced protective effect occurs in countries giving wP vaccine. Many factors affect how much protection is passed from a mother to her baby during pregnancy. A very important factor is whether or not the mum has HIV infection. Around 10% of pregnant women in Uganda have HIV and so we need to see if a mother with HIV has the same response to the whooping cough vaccine as a mother without HIV, and whether they pass the same amount of protection to their babies. We will study these important questions by asking a group of HIV-infected and HIV-uninfected pregnant women to be part of our vaccine trial. We will vaccinate half of each group with tetanus and whooping cough vaccines, and half of each with the routine tetanus vaccine, which pregnant women in Uganda already receive. We will then measure the antibody levels in the mothers' blood at the time of delivery and the antibody levels in the baby's umbilical cord blood. We can then measure how much antibody is passed from mothers to their babies. We will compare the antibody levels between HIV-negative and HIV-positive women. We will then follow-up all the babies, and measure their whooping cough antibody responses at the end of their routine vaccination course, to find out whether vaccinating their mothers has influenced the infant's protection levels.Throughout this 24 month study in Uganda we will answer the following questions to help decide whether maternal vaccination should be used to protect the most vulnerable babies in countries like Uganda:1) Do pregnant women with HIV have lower antibody responses to immunization with tetanus, diphtheria, acellular pertussis (Tdap) vaccine, compared to HIV-uninfected women?2) Does immunization with Tdap vaccine in pregnancy influence the amount of antibody an infant makes following the whole cell pertussis (wP) vaccine in babies.