Årsrapporten för övervakningen av kikhosta (pertussis) beskriver utfallet av antal rapporterade fall av kikhosta för alla åldersgrupper med förstärkt övervakning av kikhosta hos barn och ungdomar som pågått i Sverige under nitton års tid. Rapporten beskriver i detalj förekomst av kikhosta utifrån ålder, vaccinationsstatus och sjukdomsbörda med särskilt fokus på barn yngre än ett år. Rapporten är avsedd som kunskapsstöd för forskare och vårdgivare. Målgruppen för årsrapporten är hälso- och sjukvårdspersonal, och då särskilt personal inom mödravård, barnhälsovård och barnsjukvård samt primärvård och smittskyddsenheter.
For several decades there has been a 97–98% coverage of the vaccinations recommended in the National Immunisation Programme (NIP) in infancy, delivered through Sweden's well-established Child Health Clinic (CHC) system. This 19-year enhanced pertussis surveillance (EPS) has reported on the epidemiology of pertussis in Sweden at the population level since acellular pertussis (aP) was introduced in 1996. This report shows that since the introduction of aP vaccine, there has been a dramatic decline in the overall pertussis incidence in the Swedish population. However, after
years of low pertussis incidence there has been an increase in the number of reported pertussis cases in almost all age groups during the last three years, which might be an indicator of waning immunity. The increase of pertussis in 2014 was difficult to predict because it was neither preceded by a decrease in vaccination coverage nor by an obvious increase of pertussis in any age group. With the current situation, it is reasonable to believe that Sweden has passed the honeymoon period as described by de Celle's (2016).
In the present 19-year report, 647 laboratory-confirmed cases of pertussis were reported to SmiNet during 2016, of which 87 cases were among infants younger than 1 year of age. As in previous years, infants had the highest incidence (74.1 cases/100,000 person years) out of all age groups in 2016. The high incidence and high rate of hospitalisation among infants was largely in infants who contracted pertussis before they received one or two doses of vaccine. The results in this report suggest that even after one dose of a pertussis vaccine there is some protection against severe pertussis, indicating the importance of timely vaccination in infants.
Sweden has had a relatively late resurgence of pertussis, which might be due to the stable and high vaccination coverage since the introduction of aP vaccine in 1996 and to a long period without pertussis vaccine in the NIP, generating cohorts with naturally acquired immunity with longer duration of disease protection. The booster vaccination (4th dose) was administered during 2007–2012 to two birth cohorts, and this might have extended the period with low incidence among children of school age. Other age groups associated with increased and higher incidences in 2016 compared to 2015 were the 11, 13, and 17 year olds. Future EPS reports will provide data on the effectiveness of the booster dose introduced in 2016 for 14–16 year olds. Despite the existing preventive strategies for reducing pertussis cases in infants, many infants still contract the disease. Infants too young for vaccination are at the greatest risk of life-threatening pertussis, and thus effective strategies to protect the youngest infants are needed. In the case of a further increase of pertussis in infants, other preventive interventions, including recommendation of maternal vaccination, will be re-evaluated when more data on safety and interference are available, and complementary strategies might be recommended in the future.