Pertussis vaccine is a vaccine that protects against whooping cough. 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 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 other vaccines.
The acellular vaccines are more commonly used in the developed world due to fewer side 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 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.
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Medical uses
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. aP vaccines also produce less side effects.
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 put down to a combination of waning immunity and new mutations in the pathogen that existing vaccines are unable to effectively control.
Children
For children, the immunizations are commonly given in combination with immunizations against tetanus, diphtheria, polio, and haemophilus influenzae type B at ages two, four, six, and 15-18 months. 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.
Adults
In 2006 the CDC recommended adults receive pertussis vaccination along with the tetanus and diphtheria toxoid booster. In 2011 they began recommended boosters during each pregnancy. In the UK vaccination of pregnant women (between 28 and 38 weeks of pregnancy) is also recommended.
The pertussis booster for adults is combined with a tetanus vaccine and diphtheria vaccine booster; this combination is abbreviated "Tdap" (Tetanus, diphtheria, acellular pertussis). It is similar to the childhood vaccine called "DTaP" (Diphtheria, Tetanus, acellular Pertussis), with the main difference that the adult version contains smaller amounts of the diphtheria and pertussis components--this is indicated in the name by the use of lower-case "d" and "p" for the adult vaccine. The lower-case "a" in each vaccine indicates that the pertussis component is acellular, or cell-free, which reduces the incidence of side effects. The pertussis component of the original DPT vaccine accounted for most of the minor local and systemic side effects in many vaccinated infants (such as mild fever or soreness at the injection site). The newer acellular vaccine, known as DTaP, has greatly reduced the incidence of adverse effects compared to the earlier "whole-cell" pertussis vaccine, however the efficacy of the acellular vaccine declines faster than the whole-cell vaccine.
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Side effects
Between 10 and 50% of people given the whole-cell vaccines develop redness, swelling, soreness or tenderness at the injection site and/or fever, less than 1% experience febrile seizures or long periods of crying, and less than 1 out of every 1,000 to 2,000 people vaccinated have a hypotonic-hyporesponsive episode. The same reactions may occur after acellular vaccines, but are less common. Side effects with both types of vaccines, but especially the whole-cell vaccine, are less 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 WHO says that the only contraindication to either whole cell or acellular pertussis vaccines is an anaphylactic reaction to a previous dose of pertussis vaccine, while the US CDC lists encephalopathy not due to another identifiable cause occurring within seven days after a previous dose of pertussis vaccine as a contraindication and recommends those who have had seizures, have a known or suspected neurological disorder, or have had a neurologic event after a previous dose not be vaccinated until after treatment is initiated and the condition stabilized. Only the acellular vaccine is used in the US.
Modern formulations
As of 2009 there were four acellular TDaP/Tdap vaccines licensed for use in USA: Infanrix and Daptacel - for children, Boostrix and Adacel - for adolescents and adults.
History
Pertussis vaccine is usually administered as a component of the diphtheria-tetanus-pertussis (DTP) vaccines. There are several types of DTP vaccines. The first vaccine against pertussis was developed in the 1930s by pediatrician Leila Denmark. It included whole-cell killed Bordetella pertussis bacteria. Until the beginning of the 1990s it was used as a part of the DTwP vaccine for the immunization of children. It, however, contained pertussis endotoxin (surface lipooligosaccharide) and produced side effects.
New acellular pertussis vaccines were developed in the 1980s, which included only a few selected pertussis antigens (toxins and adhesins). Acellular vaccines are less likely to provoke side effects. They became a part of DTaP vaccines for children. In 2005, two new vaccine products were licensed for use in adolescents and adults that combine the tetanus and diphtheria toxoids with acellular pertussis vaccine. These (Tdap) vaccines contain reduced amounts of pertussis antigens compared to DTaP vaccines.
Both WHO and the CDC found that the acellular pertussis vaccines were effective at prevention of the disease, but had a limited impact on infection and transmission, meaning that vaccinated people could act as asymptomatic reservoirs of infection.
Source of the article : Wikipedia
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