Results confirm how uncommon known complications are as researchers confirm benefits from vaccines still ‘vastly outweigh the risks’
Two new but exceptionally rare Covid-19 vaccine side effects – a neurological disorder and inflammation of the spinal cord – have been detected by researchers in the largest vaccine safety study to date.
The study of more than 99 million people from Australia, Argentina, Canada, Denmark, Finland, France, New Zealand and Scotland also confirmed how rare known vaccine complications are, with researchers confirming that the benefits of Covid-19 vaccines still “vastly outweigh the risks”.
Researchers working as part of the Global Vaccine Data Network used deidentified electronic healthcare data to compare the rates of 13 brain, blood and heart conditions in people after they received the Pfizer, Moderna or AstraZeneca vaccine with the rate that would be expected of those conditions in the population before the pandemic.
Acute disseminated encephalomyelitis and transverse myelitis following COVID-19 vaccination - A self-controlled case series analysis - doi: 10.1016/j.vaccine.2024.01.099. https://pubmed.ncbi.nlm.nih.gov/38350771/
Abstract
Acute Disseminated Encephalomyelitis (ADEM) and Transverse Myelitis ™ are within the group of immune mediated disorders of acquired demyelinating syndromes. Both have been described in temporal association following various vaccinations in case reports and case series and have been evaluated in observational studies. A recent analysis conducted by The Global Vaccine Data Network (GVDN) observed an excess of ADEM and TM cases following the adenoviral vectored ChAdOx1 nCoV-19 (AZD1222) and mRNA-1273 vaccines, compared with historically expected background rates from prior to the pandemic. Further epidemiologic studies were recommended to explore these potential associations. We utilized an Australian vaccine datalink, Vaccine Safety Health-Link (VSHL), to perform a self-controlled case series analysis for this purpose. VSHL was selected for this analysis as while VSHL data are utilised for GVDN association studies, they were not included in the GVDN observed expected analyses. The VSHL dataset contains vaccination records sourced from the Australian Immunisation Register, and hospital admission records from the Victorian Admitted Episodes Dataset for 6.7 million people. These datasets were used to determine the relative incidence (RI) of G040 (ADEM) and G373 ™ ICD-10-AM coded admissions in the 42-day risk window following COVID-19 vaccinations as compared to control periods either side of the risk window. We observed associations between ChAdOx1 adenovirus vector COVID-19 vaccination and ADEM (all dose RI: 3.74 [95 %CI 1.02,13.70]) and TM (dose 1 RI: 2.49 [95 %CI: 1.07,5.79]) incident admissions. No associations were observed between mRNA COVID-19 vaccines and ADEM or TM. These findings translate to an extremely small absolute risk of ADEM (0.78 per million doses) and TM (1.82 per million doses) following vaccination; any potential risk of ADEM or TM should be weighed against the well-established protective benefits of vaccination against COVID-19 disease and its complications. This study demonstrates the value of the GVDN collaboration leveraging large population sizes to examine important vaccine safety questions regarding rare outcomes, as well as the value of linked population level datasets, such as VSHL, to rapidly explore associations that are identified.
Keywords: Acute Disseminated Encephalomyelitis; Adverse reactions; COVID-19; Data linkage; Transverse Myelitis; Vaccination.