Pertussis vaccine

Pertussis vaccine is a vaccine that protects against whooping cough (pertussis). There are two main types: whole-cell vaccines and acellular vaccines. The whole-cell vaccine is about 78% effective while the acellular vaccine is 71–85% effective. The effectiveness of the vaccines appears to decrease by between 2 and 10% per year after vaccination with a more rapid decrease with the acellular vaccines. Vaccinating the mother during pregnancy may protect the baby. The vaccine is estimated to have saved over 500,000 lives in 2002. The World Health Organization and Center for Disease Control and Prevention recommend all children be vaccinated for pertussis and that it be included in routine vaccinations. This includes for people who have HIV/AIDS. Three doses starting at six weeks of age are typically recommended in young children. Additional doses may be given to older children and adults. The vaccine is only available in combination with tetanus and diphtheria vaccines. The acellular vaccines are more commonly used in the developed world due to fewer adverse effects. Between 10 and 50% of people given the whole-cell vaccines develop redness at the injection site or fever. Febrile seizures and long periods of crying occur in less than 1% of people. With the acellular vaccines a brief period of non-serious swelling of the arm may occur. Side effects with both types of vaccines, but especially the whole-cell vaccine, are less common the younger the child. The whole-cell vaccines should not be used after seven years of age. Serious long term neurological problems are not associated with either type. The pertussis vaccine was developed in 1926. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. A version that also includes tetanus, diphtheria, polio, and Hib vaccine is available wholesale in the developing world at a cost of 15.41 USD per dose as of 2014. Acellular pertussis vaccine (aP) with three or more antigens prevents around 85% of typical whooping cough cases in children. It has higher or similar efficacy to the previously-used whole cell pertussis vaccine, however the efficacy of the acellular vaccine declines faster. Acellular vaccines also cause fewer side effects than whole cell vaccines. Despite widespread vaccination, pertussis has persisted in vaccinated populations and is one of the most common vaccine-preventable diseases. The recent resurgence in pertussis infections is attributed to a combination of waning immunity and new mutations in the pathogen that existing vaccines are unable to effectively control. Some studies have suggested that while acellular pertussis vaccines are effective at preventing the disease, they have a limited impact on infection and transmission, meaning that vaccinated people could spread the disease even though they may have only mild symptoms or none at all. For children, immunizations are commonly given in combination with immunizations against tetanus, diphtheria, polio, and haemophilus influenzae type B at two, four, six, and 15–18 months of age. A single later booster is given at four to six years of age (US schedule). In the UK, pertussis vaccinations are given at 2, 3, and 4 months, with a pre-school booster at 3 years 4 months.