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Background A forty-year debate on the potential negative effects of repeated seasonal influenza vaccination has been inconclusive, with multiple observational studies of various design providing heterogeneous results too inadequate to inform vaccination policy. Methods A large population-based cohort study including over one-million observations in individuals over age 65 from six consecutive seasons (2011/12–2016/17) in Stockholm County, Sweden. Current season vaccine effectiveness (VE) against severe, mostly hospital-attended, influenza was assessed using Cox multivariate regression analyses adjusting for demographic variables, comorbidities and previous seasonal influenza vaccination status. Results In none of the six seasons was VE significantly different in persons vaccinated in the current season only, compared to those who had been vaccinated in both the current and the previous season. Neither were there any differences in VE during the seasons 2014/15–2016/17 when comparing persons vaccinated during the current season only vs. those vaccinated during one-three or four-five previous influenza seasons. In contrast, persons only vaccinated during one or more previous years had no protection during the current season. Conclusions Persons above 65 years are the largest group at risk for severe or complicated influenza and policy should support their yearly seasonal influenza vaccination, which is to-date the best preventive measure available for all risk groups. No negative effects of repeated seasonal vaccination were seen in this large population-based cohort of older persons with severe influenza, which strengthens the recommendation that persons belonging to this age group should be vaccinated yearly.

Picornaviruses (family Picornaviridae) are small, nonenveloped, positive-sense, single-stranded RNA viruses. The members of this family are currently classified into 47 genera and 110 species. Of picornaviruses, entero-and parechoviruses are associated with aseptic meningitis. They are transmitted via fecal-oral and respiratory routes, and occasionally, these viruses may cause a brief viremia and gain access to central nervous system (CNS). During the diagnostic screening of entero-and parechovirus types in Finland in year 2013-14, we detected a cluster of echovirus 4 (E4) infections in young adults and adolescents. As E4 is infrequently detected in Finland, we contacted several Northern and Central European laboratories that conduct routine surveillance for enteroviruses and, for those who have had E4 cases, we send a query for E4 sequences and data. Here we report CNS infections caused by E4 in Finland, Sweden, Norway, Denmark, Iceland and Germany in 2013 and 2014, and show that the E4 detected in these countries form a single lineage. In contrast, E4 strains circulating in these countries preceding the year 2013, and those circulating elsewhere in Europe during 2013-2014, formed several independent clusters.

Here were report the increased numbers of Campylobacter detections in blood samples, first noted in July 2014, in Sweden. We investigated whether this increase was a result of a general increase in incidence of Campylobacter infections in Sweden or if the observed increase resulted from increased testing or from a change in laboratory methods. Campylobacter is the most common bacterial cause of gastroenteritis in Europe, with over 200 000 laboratoryconfirmed cases occurring yearly. Although the outcome of Campylobacter gastroenteritis is typically good, infections have been occasionally linked to systemic invasive disease and postinfectious complications. On the basis of previous studies, the incidence of campylobacteraemia varies between 0.1% and 0.4% of the total incidence of Campylobacter infections [1–3]. However, clinical significance of campylobacteraemia is poorly understood, and it has been suspected to have been an underestimated event [1,4]. To investigate whether the incidence of Campylobacter infections had generally increased in Sweden, we reviewed data on all notified Campylobacter cases (including cases of bacteraemia) between 2010 and 2014. Because of nationwide mandatory reporting, both treating physicians and clinical microbiology laboratories in Sweden (population of 9.64 million people) report all Campylobacter infections to the database maintained at the Public Health Institute of Sweden, from which a total of 39 832 cases of Campylobacter infections were identified (Fig. 1a). From those, 133 were cases of

The publisher regrets that the co-authors in the “European region influenza surveillance network” were not tagged correctly. The full and complete list of authors and their affiliations for this article is given above. The publisher would like to apologise for any inconvenience caused.

As part of our ongoing screening of wild birds in Northern Europe, 358 mallards (Anas platyrhynchos) and 203 shelducks (Tadorna tadorna) were caught in southern Sweden during the spring 2003. Faecal samples were analyzed by real time RT-PCR for the presence of influenza A virus. In contrast to what has been found in North American studies; Eurasian spring migrating ducks passing through Sweden had a relatively high prevalence of influenza A virus.