Effectiveness of COVID-19 vaccines to prevent long COVID: data from Norway

Our recent study using data from more than 20 million participants has shown that COVID-19 vaccines consistently prevent long COVID symptoms in adults, with meta-analytic calibrated subdistribution hazard ratio (sHRs) of 0·54 (95% CI 0·44–0·67) in CPRD GOLD, 0·48 (0·34–0·68) in CPRD AURUM, 0·71 (0·55–0·91) in SIDIAP, and 0·59 (0·40–0·87) in CORIVA.

In addition, when considering post-COVID thromboembolic and cardiovascular complications as outcomes of interest, recently published data have shown that vaccination with any COVID-19 first vaccine dose (ChAdOx1, BNT162b2, and mRNA-1273) is associated with reduced risk of post-acute heart failure (0·45 [0·38–0·53] 0–30 days after SARS-CoV-2 infection; 0·61 [0·51–0·73] 91–180 days after SARS-CoV-2 infection), venous thromboembolism (sHR 0·22 [95% CI 0·17–0·29] 0–30 days after SARS-CoV-2 infection; 0·53 [0·40–0·70] 91–180 days after SARS-CoV-2 infection), and arterial thrombosis (0·53 [0·44–0·63] 0–30 days after SARS-CoV-2 infection; 0·72 [0·58–0·88] 91–180 days after SARS-CoV-2 infection).

With the use of the Observational Medical Outcomes Partnership (OMOP) common data model (CDM), all our analyses were conducted across three European countries (Estonia, Spain, and the UK) without transferring patient data, using federated analyses similar to those used by the European Medicines Agency-funded Data Analysis and Real World Interrogation Network.

Here, we show further reproducibility and report results from applying the same analyses to the Norwegian Linked Health Registries at University of Oslo, covering the entire Norwegian population of approximately 5·4 million inhabitants. Data from six registries covering primary and secondary care, hospitalisations, vaccinations, communicable disease notifications, prescriptions, and sociodemographic factors between 2018 and 2021 were mapped to the OMOP CDM. Reproducing previous methods (appendix p 25 and our previous study),

we generated four study cohorts in line with the Norwegian vaccination campaign rollout between Jan 9, 2021, and Aug 6, 2021: people aged 75 years and older (cohort one); 65 years and older and clinically extremely vulnerable people, and those with underlying health conditions aged 18 years and older (cohort two); 18 years and older with underlying conditions (cohort three); and 18 years and older (cohort four; appendix p 3). We then applied the publicly available scripts to assess the effectiveness of COVID-19 vaccines to prevent long COVID and post-acute complications.

A total of 2 364 651 vaccinated and 1 532 935 unvaccinated individuals in Norway were included (appendix p 18). Of the vaccinated individuals, 1576 (0·09%) developed at least one of the 25 WHO-listed symptoms recorded at between 90 and 365 days after the date of a COVID-19 positive test or diagnosis, with no record of that symptom 180 days before SARS-Cov-2 infection, and were therefore identified as long COVID cases, compared with 2922 (0·17%) of the unvaccinated individuals (table). Background characteristics of the study population by cohorts are presented in the appendix (p 4). Adequate covariate balance between the vaccinated and unvaccinated groups was achieved after weighting, as shown in the appendix (p 6). Information regarding follow-up time and censoring information are summarised in the appendix (p 8).