Whooping cough or pertussis, is a vaccine preventable infection. It is of global public health importance and is the most common vaccine preventable cause of death in children under the age of one year in the United Kingdom (Amirthalingam 2013).
Whooping cough is a very infectious and occasionally fatal infection caused by the bacteria Bordatella pertussis. It is transmitted by respiratory droplets, with an incubation period of between 6 and 20 days. Whooping cough starts with a catarrhal phase, followed by an irritating cough over the next one to two weeks. The cough progressively becomes paroxysmal and is often followed by a characteristic inspiratory “whoop” and sometimes vomiting. In infants, the inspiratory “whoop” may be absent, instead the paroxysmal cough is followed by periods of apnoea. Whooping cough can be very protracted, lasting weeks or even months, in China whooping cough is known as “the cough of 100 days” (Carbonetti 2007). Comparatively minor complications include sub-conjunctival haemorrhage, facial oedema, nose bleeds, mouth ulcers and otitis media. However serious complications can occur and these are more common in infants under 6 months of age, including apnoea, pneumonia, weight loss, cerebral hypoxia and death.
Prior to the introduction of an immunisation programme against whooping cough in the UK in 1957, there were around 120,000 cases of whooping cough per year in the UK (Public Health England 2016). By the mid-1990s, over 90% of children aged two years had completed primary courses of pertussis containing vaccine immunisation (three doses). The high level of vaccine uptake led to disease notifications falling to 1,500 cases or less per year for the period 2000-2011 (Public Health England 2016). Vaccines against whooping cough are routinely given to babies in the UK at 8, 12 and 16 weeks of age with a pre-school booster dose at 3 years and 4 months.
During 2011 there was an increase in the number of cases of whooping cough infection and over 9700 confirmed cases, mainly in adolescents and adults reported in England and Wales during 2012 (Health Protection Agency 2012). Cases of whooping continued to be reported at elevated levels during 2012, that year there were 14 deaths, all in infants all under 3 months of age and therefore too young to have been fully protected against pertussis through routine childhood immunisation (Amirthalingam 2013).
As a result of these infant fatalities, an immunisation programme was introduced in 2012 to offer a whooping cough containing vaccine to all pregnant women between 28 and 38 weeks gestation with the optimal time to give the vaccine being between 28 and 32 weeks (Chief Medical Officer 2012).
Since whooping cough vaccine was introduced for pregnant women, further research on the optimal time to administer it has been conducted (Eberhardt 2016), which has led the vaccine now being offered in the UK from 16 weeks gestation although or operational reaons it is often offered just after the fetal anomaly scan. The vaccine can now be given from 16 weeks up to the point of labour; however whooping cough vaccine given in late pregnancy may be less effective at protecting the neonate. The optimal time to immunise pregnant women against whooping cough is between 16 and 32 weeks gestation (Public Health England 2016).
The aim of the pre-natal whooping cough immunisation programme is to boost maternal whooping cough antibodies so that they cross the placental barrier in the last trimester of pregnancy, thus providing the baby with passive immunity to infection with pertussis from birth. The programme is designed to complement the active protection a baby will get from routine immunisations starting at 8 weeks of age, by ensuring the neonate also has passive protection from birth. Whooping cough antibodies decline over time and women should be offered the vaccine in each pregnancy, from 16 weeks gestation. Only one dose of whooping cough vaccine is required per pregnancy, regardless of the number of foetuses per pregnancy.
When given in pregnancy, the vaccine is very effective preventing whooping cough in the first 3 months of life of infants. Vaccine efficacy has been estimated to be between 91% and 93% (Amirthalingam 2014, Dabrera 2014).
Uptake of whooping cough vaccine in pregnancy in England has steadily improved since its introduction in 2012. In the first year of the programme, from October 2012 to September 2013, uptake ranged from 43% to 59% (Public Health England 2013). Pertussis vaccine coverage increased from 73.8% in October 2016 to 76.2% in December 2016. Coverage in October and December in 2016 was 14.2% higher than that observed for the October to December period in 2015 (Public Health England 2017).
Whilst the introduction of the immunisation programme in pregnancy has reduced deaths in neonates, whooping cough fatalities have still occurred, mainly in babies whose mothers were not immunised in pregnancy, or who received the vaccine too late pregnancy for it to have been effective. It is therefore important that all pregnant women are offered pertussis immunisation from the 16th week of pregnancy. During the influenza season, which runs from approximately September to February, influenza vaccine can be administered at the same time as pertussis vaccine. As influenza vaccine can be given at any stage of pregnancy, it is not necessary to delay influenza vaccine until the woman is eligible for pertussis vaccine.
As there is no single antigen whooping cough vaccine available, the vaccine used in the UK (Boostix IPV) also contains protection against tetanus, diphtheria and polio. All of the vaccine components are inactivated (killed) and can be safely given in pregnancy.
Medicines administered in pregnancy may have harmful effects on the embryo or foetus (BNF 2014). Whilst the whooping cough containing vaccine does have side effects, commonly pain, redness and swelling at the injection site (Electronic Medicines Compendium 2015), a study of over 20,000 women who received pertussis containing vaccine in pregnancy found “no evidence of an increased risk of any of an extensive predefined list of adverse events related to pregnancy” (Donegan 2014).
In the UK midwives are considered to be the “key professionals” in guaranteeing that pregnant women have a safe pregnancy, childbirth and post-natal period (Chief Nursing Officers 2010). A recent study found that 96% of women would definitely or probably accept a vaccine in pregnancy to protect their baby and that 90% would ideally like information about the vaccine from their midwife (Campbell 2015). This key finding suggests that whilst vaccine uptake is improving, they may be opportunity to increase it further.
The delivery model for the administration of the pertussis containing vaccine in pregnancy is likely to vary depending local commissioning arrangements. In some cases the midwife or other health professional may administer the vaccine during routine antenatal care, or in others signpost the pregnant woman to her general practice to receive it. Irrespective of the local delivery model, pregnant women should be made aware of the risks to their baby from pertussis infection and be able to access the vaccine should they wish to receive it.
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