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Change in risk for narcolepsy over time and impact of definition of onset date following vaccination with AS03 adjuvanted pandemic A/H1N1 influenza vaccine (Pandemrix) during the 2009 H1N1 influenza pandemic.
Pharmacoepidemiol Drug Saf. 2019 08; 28(8):1045-1053.PD

Abstract

PURPOSE

To estimate risk for narcolepsy in defined time windows following exposure to adjuvanted A(H1N1) pandemic vaccine (Pandemrix) and impact of different definitions of index date for the narcolepsy diagnosis.

METHODS

Vaccine exposure in approximately 30% of the Swedish population in 2009 was linked to information on narcolepsy diagnosis retrieved from the national patient registry. Cases were verified by a systematic chart review. Poisson regression was used to compare incidence in defined time windows following vaccination.

RESULTS

Of 266 cases of narcolepsy identified, 25% (66/266) were prevalent cases with symptom onset documented before vaccine exposure. Incident cases had a median time interval between first symptom and the date recorded in the patient registry of 64 weeks (IQR 39-107) when vaccinated (N = 182) and 65 weeks (IQR 51-72) when unvaccinated (N = 16). With first symptom defining index date, the adjusted risk for narcolepsy in younger patients was increased 14 times during the first year after vaccination, three times elevated the second year, but with no detectable increased risk more than 2 years after vaccination exposure. Using the index date from the patient registry, the adjusted increase in risk was about seven times elevated for all three time intervals.

CONCLUSIONS

The magnitude of the estimated increased risk for narcolepsy following exposure to the A(H1N1) pandemic vaccine is highly dependent on the method used to determine the index date for disease onset. The sometimes very long and potentially variable interval from first symptom to a health care registry diagnosis complicates estimations of risk.

Authors+Show Affiliations

Clinical Epidemiology Division, Department of Medicine Solna, Karolinska Institute, Stockholm, Sweden.Department of Efficacy and Safety 1, Medical Products Agency, Uppsala, Sweden.Department of Women's and Children's Health, Karolinska Institute, Stockholm, Sweden.Department of Scientific Expertise, Medical Products Agency, Uppsala, Sweden.

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

31062443

Citation

Granath, Fredrik, et al. "Change in Risk for Narcolepsy Over Time and Impact of Definition of Onset Date Following Vaccination With AS03 Adjuvanted Pandemic A/H1N1 Influenza Vaccine (Pandemrix) During the 2009 H1N1 Influenza Pandemic." Pharmacoepidemiology and Drug Safety, vol. 28, no. 8, 2019, pp. 1045-1053.
Granath F, Gedeborg R, Smedje H, et al. Change in risk for narcolepsy over time and impact of definition of onset date following vaccination with AS03 adjuvanted pandemic A/H1N1 influenza vaccine (Pandemrix) during the 2009 H1N1 influenza pandemic. Pharmacoepidemiol Drug Saf. 2019;28(8):1045-1053.
Granath, F., Gedeborg, R., Smedje, H., & Feltelius, N. (2019). Change in risk for narcolepsy over time and impact of definition of onset date following vaccination with AS03 adjuvanted pandemic A/H1N1 influenza vaccine (Pandemrix) during the 2009 H1N1 influenza pandemic. Pharmacoepidemiology and Drug Safety, 28(8), 1045-1053. https://doi.org/10.1002/pds.4788
Granath F, et al. Change in Risk for Narcolepsy Over Time and Impact of Definition of Onset Date Following Vaccination With AS03 Adjuvanted Pandemic A/H1N1 Influenza Vaccine (Pandemrix) During the 2009 H1N1 Influenza Pandemic. Pharmacoepidemiol Drug Saf. 2019;28(8):1045-1053. PubMed PMID: 31062443.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Change in risk for narcolepsy over time and impact of definition of onset date following vaccination with AS03 adjuvanted pandemic A/H1N1 influenza vaccine (Pandemrix) during the 2009 H1N1 influenza pandemic. AU - Granath,Fredrik, AU - Gedeborg,Rolf, AU - Smedje,Hans, AU - Feltelius,Nils, Y1 - 2019/05/06/ PY - 2018/10/03/received PY - 2019/03/11/revised PY - 2019/03/25/accepted PY - 2019/5/8/pubmed PY - 2020/5/22/medline PY - 2019/5/8/entrez KW - H1N1 subtype KW - adverse effects KW - influenza A virus KW - mass vaccination KW - narcolepsy KW - pandemics KW - pharmacoepidemiology KW - vaccination SP - 1045 EP - 1053 JF - Pharmacoepidemiology and drug safety JO - Pharmacoepidemiol Drug Saf VL - 28 IS - 8 N2 - PURPOSE: To estimate risk for narcolepsy in defined time windows following exposure to adjuvanted A(H1N1) pandemic vaccine (Pandemrix) and impact of different definitions of index date for the narcolepsy diagnosis. METHODS: Vaccine exposure in approximately 30% of the Swedish population in 2009 was linked to information on narcolepsy diagnosis retrieved from the national patient registry. Cases were verified by a systematic chart review. Poisson regression was used to compare incidence in defined time windows following vaccination. RESULTS: Of 266 cases of narcolepsy identified, 25% (66/266) were prevalent cases with symptom onset documented before vaccine exposure. Incident cases had a median time interval between first symptom and the date recorded in the patient registry of 64 weeks (IQR 39-107) when vaccinated (N = 182) and 65 weeks (IQR 51-72) when unvaccinated (N = 16). With first symptom defining index date, the adjusted risk for narcolepsy in younger patients was increased 14 times during the first year after vaccination, three times elevated the second year, but with no detectable increased risk more than 2 years after vaccination exposure. Using the index date from the patient registry, the adjusted increase in risk was about seven times elevated for all three time intervals. CONCLUSIONS: The magnitude of the estimated increased risk for narcolepsy following exposure to the A(H1N1) pandemic vaccine is highly dependent on the method used to determine the index date for disease onset. The sometimes very long and potentially variable interval from first symptom to a health care registry diagnosis complicates estimations of risk. SN - 1099-1557 UR - https://www.unboundmedicine.com/medline/citation/31062443/Change_in_risk_for_narcolepsy_over_time_and_impact_of_definition_of_onset_date_following_vaccination_with_AS03_adjuvanted_pandemic_A/H1N1_influenza_vaccine__Pandemrix__during_the_2009_H1N1_influenza_pandemic_ L2 - https://doi.org/10.1002/pds.4788 DB - PRIME DP - Unbound Medicine ER -