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- Askling, Helena Hervius
(författare)
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Infectious diseases in returning Swedish travellers
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The number of travellers to “tropical” parts of the world has increased substantially during the past decades. Identifying risk groups and providing preventive measures is important both to reduce the number of travellers falling ill and to prevent introduction of diseases into new countries. The aim of this thesis is to describe the epidemiology of imported infectious diseases in Sweden and to identify risk groups. To investigate epidemiology and use of chemoprophylaxis in patients notified with P.falciparum malaria we studied compiled information on patients notified to the Swedish institute for infectious disease control (SMI) 1994-2001. Ninety percent of the patients had traveled to Africa. Malaria infection despite intake of adequate chemoprophylaxis decreased during the study period indicating more effective chemoprophylaxis at the later part of the study. Chloroquine/proguanil had been prescribed for travellers to Africa when it was no longer in line with the national recommendation. To evaluate risk groups for malaria, we conducted an observational analytic study on all malaria cases notified to SMI 1997-2003 and compared them with data from the Swedish tourist and travel database (TDB). Malaria was more often diagnosed in men than in women (OR 1.7, 95% CI 1.3-2.3), in the age group 0-6 years (OR 4.8, 95% 1.5- 14-8) and in travellers to sub Saharan Africa. To evaluate the effectiveness and adverse events (AE) of malaria chemoprophylaxis in a high transmission area, we studied compiled information from Swedish soldiers (7,000 person months) in Liberia. The majority (81%) of the soldiers took mefloquine and the remaining part atovaquone/proguanil. After return to Sweden all soldiers completed a questionnaire about behavior and AE. No cases of P. falciparum malaria were notified. The AE were mostly mild. To estimate risk groups for travel related hepatitis A infection in Sweden 1997-2005 we used notification data from SMI as nominator and TDB as a denominator. The highest incidence was seen in the age-group 0-6 years and in travellers to east Africa, Middle East and India where a majority of the travellers had been going to see friends and relatives in their country of origin (VFR-travellers). To investigate causes of travel related fever we included febrile patients returning from malaria endemic areas to five Swedish hospitals 2005-2008. Additional paired sera were analyzed for influenza virus, dengue virus, chikungunya virus, Brucella spp., Leptospira spp., C.burnetii, and Rickettsia spp. In 21% of patients with unknown fever additional serology revealed a diagnosis. In 9% patients with a defined diagnosis, additional serology established a co-infection. Influenza was the most common serological finding followed by dengue fever, rickettsial infections and leptospirosis. Conclusion: The chief problem with malariaprophylaxis is the failure to use them when really needed. VFR-travellers, and especially their children, constitute a high risk group for malaria and hepatitis A and preventive measures should be focused on this group. Influenza is an underestimated cause of fever in travellers returning from sub/tropical regions.
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| 3. |
- Erra, Elina O, et al.
(författare)
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A single dose of vero cell-derived Japanese encephalitis (JE) vaccine (Ixiaro) effectively boosts immunity in travelers primed with mouse brain-derived JE vaccines
- 2012
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Ingår i: Clinical Infectious Diseases. - : Oxford University Press (OUP). - 1058-4838 .- 1537-6591. ; 55:6, s. 825-834
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND:A significant part of the world population lives in areas with endemic Japanese encephalitis (JE). For travelers from nonendemic countries, Vero cell-derived vaccine (JE-VC; Ixiaro) has replaced traditional mouse brain-derived vaccines (JE-MB) associated with safety concerns. The 2 vaccines are derived from different viral strains: JE-VC from the SA14-14-2 strain and JE-MB from the Nakayama strain. No data exist regarding whether JE-VC can be used to boost immunity after a primary series of JE-MB; therefore, a primary series of JE-VC has been recommended to all travelers regardless of previous vaccination history.METHODS:One hundred twenty travelers were divided into 4 groups: Volunteers with no prior JE vaccination received primary immunization with (group 1) JE-MB or (group 2) JE-VC, and those primed with JE-MB received a single booster dose of (group 3) JE-MB or (group 4) JE-VC. Immune responses were tested before and 4-8 weeks after vaccination using plaque reduction neutralization test (PRNT) against both vaccine strains.RESULTS:In vaccine-naive travelers, the vaccination response rate for test strains Nakayama and SA14-14-2 was 100% and 87% after primary vaccination with JE-MB and 87% and 94% after JE-VC, respectively. Antibody levels depended on the target virus, with higher titers against homologous than heterologous PRNT(50) target strain (P < .001). In travelers primed with JE-MB, vaccination response rates were 91% and 91%, and 98% and 95% after a booster dose of JE-MB or JE-VC, respectively. Subgroup analysis revealed that a higher proportion of primed (98%/95%) than nonprimed (39%/42%) volunteers responded to a single dose of JE-VC (P < .001).CONCLUSIONS:A single dose of JE-VC effectively boosted immunity in JE-MB-primed travelers. Current recommendations should be reevaluated.CLINICAL TRIALS REGISTRATION:NCT01386827.
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| 4. |
- Erra, Elina O., et al.
(författare)
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Cross-protection elicited by primary and booster vaccinations against Japanese encephalitis : A two-year follow-up study
- 2013
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Ingår i: Vaccine. - : Elsevier BV. - 0264-410X .- 1873-2518. ; 32:1, s. 119-123
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Tidskriftsartikel (refereegranskat)abstract
- Background: The inactivated Vero cell-derived vaccine (JE-VC, IXIARO) has replaced the traditional mouse brain-derived preparations (JE-MB) in travelers' vaccinations against Japanese encephalitis. We showed recently that a single JE-VC dose efficiently boosts immunity in JE-MB-primed vaccinees, and that JE-VC elicits cross-protective immunity against non-vaccine genotypes, including the emerging genotype I. While these studies only provided short-term data, the present investigation evaluates the longevity of seroprotection in the same volunteers.Methods:The study comprised 48 travelers who had received (1) JE-VC primary series, (2) JE-MB primary series followed by a single JE-VC booster dose, or (3) JE-MB primary series and a single JE-MB booster dose. Serum samples were collected two years after the last vaccine dose, and evaluated with the plaque-reduction neutralization test against seven Japanese encephalitis virus strains representing genotypes I-IV. PRNT50 titers >= 10 were considered protective.Results:Two years after the primary series with JE-VC, 87-93% of the vaccinees proved to be cross-protected against test strains representing genotypes II-IV and 73% against those of genotype I. After a single homologous or heterologous booster dose to JE-MB-primed subjects, the two-year seroprotection rates against genotype I-IV strains were 89-100%.Conclusions:After JE-VC primary series, seroprotection appeared to wane first against genotype I. The first booster should not be delayed beyond two years. In JE-MB-primed subjects, a single JE-VC booster provided cross-protective immunity against genotype I-IV strains in almost all vaccinees, suggesting an interval of two years or even longer for the second booster. These data further support the use of a single JE-VC dose for boosting JE-MB immunity.
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| 5. |
- Erra, Elina O, et al.
(författare)
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Cross-protective capacity of Japanese encephalitis (JE) vaccines against circulating heterologous JE virus genotypes
- 2013
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Ingår i: Clinical Infectious Diseases. - : Oxford University Press (OUP). - 1058-4838 .- 1537-6591. ; 56:2, s. 267-270
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Tidskriftsartikel (refereegranskat)abstract
- Current Japanese encephalitis vaccines are derived from strains of genotype III, yet heterologous genotypes are emerging in endemic areas. Inactivated vaccines given to European travelers were found to elicit protective levels of neutralizing antibodies against heterologous strains of genotypes I-IV.
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| 7. |
- Rosdahl, Anja, 1972-
(författare)
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The impact of viral vaccines in immunosuppressed and at-risk individuals
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Vaccines have saved millions of lives, but for some individuals with a defective immune system the protection may be uncertain. This thesis aims to assess the immune response following viral vaccines in immunocompromised patients and in other groups at-risk.In paper I the immune response to a modified vaccine schedule against hepatitis A, adding an extra vaccine dose, was tested in patients with rheumatoid arthritis (RA) on immunomodulating drugs. Following two doses,88% of RA patients developed seroprotective antibodies against hepatitis A compared to 94% of healthy controls. In paper II 53 cases of Tick borne encephalitis (TBE) vaccine failure were characterized. The majority of cases were seen in men, 81% were 50 years or older and 51% had co-morbidities. Vaccine failure was most common after three or four doses only, but was seen in up to nine doses. Four out of five had a moderate to severe disease. In paper III the immune response to mRNA vaccines was compared in SARS-CoV-2 experienced and naïve health care workers. Experienced individuals had an increased innate immune cell activation, cytokine and chemokine production and changes in innate gene expression following the first vaccine dose as well as a stronger adaptive response with higher antibody titres and B-cell and CD4+ T-cell activity. The differences were less after the second dose, but three doses were required before an equal immune response was observed in naïve and experienced individuals. In paper IV the immune response to SARS-CoV-2 mRNA vaccine was assessed in patients with chronic kidney disease (CKD) stage 4 and 5 prior to renal replacement therapy. CKD patients were found to have an immune response comparable with healthy controls, with the exception of lower secreted anti-spike antibodies in the saliva and a decreased cytotoxic CD8+ T-cell activity.In conclusion, a deeper understanding of the immune response to vaccines is needed to be able to adapt recommendations and improve outcome in vulnerable groups
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