Bombshell Large Observational Study—10+M Vaccinated Multi-National Study: COVID Vaccine Helps Prevent Long COVID

Researchers affiliated with the University of Oxford designed a staggered cohort study based on real-world data linked to primary care records in both the United Kingdom and Spain, as well as Estonian national health claims data. A series of data including vaccination status was employed and analyzed against time-varying exposure, staged by vaccine rollout period. The authors further sliced and diced data by vaccine brand based on their first dose. Then, defining long COVID based on at least one World Health Organization (WHO)-based symptoms post-COVID-19 infection and no history of any such symptoms in the previous 180 days, the authors applied propensity scores weighting across cohorts in a bid to minimize any confounding. The researchers also calculated sub-distribution Hazard Ratios (sHR) in an attempt to estimate vaccine effectiveness against long COVID, further using Negative Control Outcomes, empirically calibrated, in a bid to minimize residual confounding. Finally, the authors pooled their overall effect estimates via random effects meta-analyses across staged cohorts. The analyses led to the conclusion that COVID-19 vaccination reduces the risk of long COVID incidence, thus reiterating the importance of COVID-19 vaccination.

Uploaded to The Lancet preprint, the study’s corresponding author is Prof. Daniel Prieto-Alhambra. Further peer review will be needed and although the authors take measures to reduce bias, such observational studies are subject to myriad limitations. Any results should be interpreted cautiously. This output cannot be considered evidence as of yet—it’s not peer-reviewed.