Pertussis vaccines
Pertussis vaccines
There are currently two categories of pertussis vaccines, i.e. acellular and whole-cell vaccines 37. Acellular vaccines are developed from one or more highly purified individual pertussis antigens and whole-cell vaccines are based on killed Bordetella pertussis organisms. Although infants below three months of age are at the highest risk of death from Bordetella pertussis, current epidemiological evidence shows that it is an important cause of respiratory disease in both adolescents and adults 37,38,39. Despite the availability of vaccines and adequate coverage of childhood vaccinations, incidence of the disease continues to increase in adolescents and adults, possibly due to waning immunity. There are very few studies of adolescent and adult pertussis in the HIV-infected population with most of the data on pertussis coming from children 40. Maternal carriage, HIV-exposure of young infants and incomplete vaccination seem to be the most important risk factors for childhood pertussis. Available evidence indicates that maternal vaccination offers significant protective benefits to both mothers and infants 38.
Evidence shows that asymptomatic pertussis infection is more common than symptomatic infection in healthy adolescents and adults 41. More data are needed to understand the epidemiology and the burden of pertussis in countries where HIV/AIDS is endemic. To date, there are no studies with regards to the immunogenicity or efficacy of pertussis vaccination in HIV-infected adults. Evidence from studies in children demonstrates that HIV infection lowers antibody response following vaccination and high CD4+ counts at vaccination improves antibody response 40. With the lack of data on the burden of disease in HIV-infected adolescents and adults, the recommendation would be that only pregnant women, regardless of CD4+ counts or viral load, be vaccinated (with acellular vaccine) during each pregnancy until there is more evidence to do otherwise. This is mainly to increase their antibody levels, so as to enhance transplacental antibody transfer to their newborns, who are at high risk of pertussis illness 42.