Page 11 - Preventing pertussis in early infancy - Visser
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protection against new pertussis infections. After approximately 4-20 years patients are again susceptible for pertussis infection (Wendelboe et al. 2005, Crowcroft et al. 2006).
The severity of the clinical manifestation of pertussis can vary widely. Mild cases are seen among adults, among those who were previously infected by pertussis, among vaccinated individuals and among patients without co-infections. Mild cases may manifest as an ongoing simple cough, without the typical paroxysms, ‘whooping’ sound or vomiting. Among adults, the most frequently reported complications include insomnia, weight loss and urinary incontinence (Tozzi et al. 2003, Ward et al. 2005, Kilgore et al. 2016). For young infants however, pertussis can be a dangerous disease. They are too young to be fully protected by their childhood vaccinations and maternal antibodies are not sufficient without maternal vaccination. Furthermore, they are at the highest risk of severe disease and clinical complications. They may show non-specific symptoms such as feeding problems or failure to thrive in the catarrhal stage, and instead of coughing present with apnoea or cyanosis. Complications of pertussis in infants include pneumonia, convulsions, respiratory failure or even death. Hospitalisation is necessary for 50%-60% of infants under six months of age with pertussis (de Greeff et al. 2010, Kilgore et al. 2016, van der Maas et al. 2017).
Epidemiology and vaccination
Before the 1950s, pertussis was one of the most common childhood diseases worldwide, causing an estimated 4000 deaths each year in the USA (3.2/100,000) and 350 in the Netherlands (3.5/100,000). The first pertussis vaccines became available in the 1950s. This was a whole-cell vaccine, which was based on killed and detoxified whole bacteria. Although incidences of pertussis were already decreasing, the introduction of infant vaccination programmes contributed to a steep decline in the number of pertussis cases and deaths (Miller 2014).
After about twenty years of vaccination with high coverage, when pertussis infections where less frequently seen, concerns arose about possible side effects of the whole-cell vaccination which had been reported in some countries such as Japan. Although research could not find a causal relation between the vaccination and the events that had been reported, the resulting public and professional anxiety had its consequences. In Sweden and Japan, for example, the whole-cell vaccination was banned at the end of the 1970s (Gangarosa et al. 1998). In the Netherlands, it was decided to decrease the vaccine potency of the whole-cell vaccination by reducing the amount of active ingredients. At the same time, the safety concerns led to the development of acellular pertussis vaccines, which consists of specific purified B. pertussis antigens.
In the mid-nineties of the twentieth century, several countries (including the USA, the UK and the Netherlands) reported a resurgence of pertussis, after many years of a relatively low incidence (Crowcroft et al. 2006, Burns et al. 2014). This meant that despite the global vaccination efforts, with still a high coverage in many countries, pertussis was again an endemic disease in both developing and developed countries. Nowadays, pertussis epidemic cycles typically occur every 2 to 5 years and cause considerable morbidity and mortality
General Introduction
General introduction
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