ABSTRACT
Structured AbstractO_ST_ABSObjectiveC_ST_ABSIt has been hypothesized that SARS-CoV-2 infection in children can increase risk of developing type 1 diabetes. Research Design and MethodsWe undertook a prospective analysis based on all children in Denmark where we investigated the association between SARS-CoV-2 infection and subsequent risk of type 1 diabetes, using information from several different national Danish registers. Denmark had one of the highest test-rates per capita in the world during the pandemic. ResultsWe did not observe a higher risk of a first time diagnosis of type 1 diabetes in children 30 days or more after a positive SARS-CoV-2 test, compared to children with a history of only negative SARS-CoV-2 tests (Hazard ratio 0.85, 95% CI 0.70, 1.04). ConclusionsOur data do not support that SARS-CoV-2 infection is associated with type 1 diabetes, or that type 1 diabetes should be a special focus after a SARS-CoV-2 infection in children. Article HighlightsO_ST_ABSWhy did we undertake this study?C_ST_ABSO_LIStudies have shown an association between SARS-CoV-2 infection and subsequent risk of type 1 diabetes, supporting the possibility of a viral etiology in type 1 diabetes and adding to concerns regarding adverse health consequences of COVID-19. C_LI What is the specific question(s) we wanted to answer?O_LIIs the risk of new onset type 1 diabetes increased among children in the period after SARS-CoV-2 infection? C_LI What did we find?O_LIWe estimated the relative risk of being diagnosed with type 1 diabetes after a positive compared to a negative SARS-CoV-2 test, to 0.85 (95% CI 0.70, 1.04). C_LI What are the implications of our findings?O_LIOur data do not support an association between SARS-CoV-2 infection and subsequent risk of type 1 diabetes among children. C_LI Twitter SummaryA study based on all children in Denmark does not show any association between #SarsCoV2 infection and subsequent risk of #Type1Diabetes among persons < 18 years. #Type1Diabetes should not be a special focus after a #SarsCoV2 infection in children.
ABSTRACT
IntroductionIndividuals with a prior severe acute respiratory corona virus 2 (SARS-CoV-2) infection have a moderate to high degree of protection against reinfection, though seemingly less so when the Omicron variant of SARS-CoV-2 started to circulate. The aim of this study was to evaluate the vaccine effectiveness (VE) against SARS-CoV-2 reinfection, that is, in individuals with prior SARS-CoV-2 infection, during periods with different dominant SARS-CoV-2 variants. MethodsA nationwide cohort study design including all individuals with a confirmed SARS-CoV-2 infection, who were alive and residing in Denmark between 1 January 2020 and 31 January 2022 were used. Using Danish nationwide registries, we obtained information on SARS-CoV-2 infections, Coronavirus Disease 2019 (COVID-19) vaccination, age, sex, comorbidity, staying at hospital and region of affiliation. The study population included were individuals with prior SARS-CoV-2 infection. Crude and adjusted estimates of VE against SARS-CoV-2 reinfection with 95% confidence intervals (CIs) were calculated using Poisson and Cox regression models, respectively. The VE estimates were calculated separately for three periods with different dominant SARS-CoV-2 variants (Alpha (B.1.1.7), Delta (B.1.617.2), or Omicron (B.1.1.529)) and by time since vaccination using unvaccinated as the reference. FindingsThe study population comprised of 209,814 individuals infected before or during the Alpha period, 292,978 before or during the Delta period and 245,530 before or during the Omicron period. Of these, 40,281 individuals had completed their primary vaccination series during the Alpha period (19.2%), 190,026 during the Delta period (64.9%) and 158,563 during the Omicron period (64.6%). VE against reinfection following any COVID-19 vaccine type administered in Denmark, peaked at 85% (95% CI: 37% to 97%) at 104 days or more after vaccination during the Alpha period, 88% (95% CI: 81% to 92%) 14-43 days after vaccination during the Delta period and 60% (95% CI: 58% to 62%) 14-43 days after vaccination during the Omicron period. Waning immunity was observed, and was most pronounced during the Omicron period. InterpretationThis study shows that, in previously infected individuals, completing a primary vaccination series was associated with a significant protection against SARS-CoV-2 reinfection compared with no vaccination for all three variant periods. Even though vaccination seems to protect to a lesser degree against reinfection with the Omicron variant, these findings are of public health relevance as they show that previously infected individuals still benefit from COVID-19 vaccination in all three variant periods.
