Vaccinated patients hospitalized with COVID-19 in Norway spend fewer days in the hospital

Vaccination is the only solution to reduce the burden of coronavirus disease (COVID-19) on global healthcare systems in the present day. Various messenger ribonucleic acid (mRNA) and vector-based vaccines have been administered globally after emergency approval by regulatory bodies to reduce the burden of severe disease, hospitalization, and death.

Study: Patient trajectories among hospitalised COVID-19 patients vaccinated with an mRNA vaccine in Norway: a register-based cohort study. Image Credit: Medical-R / Shutterstock.com

Background

To a certain extent, the extensive vaccination program across the world have successfully reduced the severity of disease and continue to provide the best line of defense against COVID-19. However, several reports of breakthrough infection among those fully vaccinated have been a source of concern for public health authorities.

A majority of these infections are due to a rise in mutations in the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with hospitalizations often arising in those with comorbidities or old age. Multiple studies are currently being conducted to assess the efficacy of available vaccines as a result of the rise in breakthrough infection cases.

Vaccinations in Norway began on December 27, 2020, with two mRNA vaccines including the Comirnaty and Spikevax vaccines. Since then, vaccination coverage has steadily increased, with 84% of the total population being fully vaccinated with the recommended double dose by September 2021. A third booster dose has been offered to all elderly people older than 65 years and care home residents since early October 2021.

Norwegian researchers recently published a report on the preprint server medRxiv* linking individual-level data from national registries to estimate the length of stay (LoS) in hospitals, with and without intensive care unit (ICU) stay, odds of ICU admission, and in-hospital mortality among COVID-19 patients older than 18 years in Norway who had been vaccinated with an mRNA vaccine as compared to unvaccinated patients.

About the study

A total of 2,569 hospitalized patients with COVID-19 as the main cause of hospitalization not more than two days before and less than 28 days after a positive SARS-CoV-2 test was obtained from national public health registries.

The researchers excluded 154 patients vaccinated with one dose, those who were admitted less than 21 days before testing positive for COVID-19, five patients vaccinated with non-mRNA vaccines, and one unvaccinated patient who had been reinfected with SARS-CoV-2. Another patient who was admitted to the ICU due to assumed incomplete reporting on hospital stays was also excluded.

Taken together, a total of 2,361 patients were included in the final study cohort. Of these patients, 421 (18%) had been admitted to the ICU. At the end of the follow-up period, 18 patients (0.8%) were still admitted to hospital.

Of the 2,343 patients who had been discharged, 107 died in hospital (4.6%). 70 patients (3.0%) were partially vaccinated, and 183 (7.8%) were fully vaccinated. Most patients received Comirnaty (84% among partially vaccinated, 93% among fully vaccinated).

The median time from the last dose to diagnosis was 44 days for partially vaccinated and 126 days for fully vaccinated. Age and the frequency of certain underlying risk factors such as cancer, chronic lung disease, heart disease, immunocompromised status, and kidney disease increased from unvaccinated to partially vaccinated to fully vaccinated patients.

The results suggested that fully vaccinated patients over the age of 18 had an overall shorter LoS in hospital and lower odds of ICU admission when compared to unvaccinated patients. This was driven by the age group 18–79 years.

When the analysis was restricted to only patients not admitted to the ICU, there was no observed difference in the LoS between fully vaccinated and unvaccinated patients. Similar estimates were observed when collectively comparing partially and fully vaccinated patients to unvaccinated patients.

Estimates for patients between 18–64 years and 65–79 years tended in the same direction as patients 18–79 years; however, statistical significance in adjusted models was only observed for the LoS in hospital stay for patients between 18–64 years and for the odds of ICU admission for patients between 65–79 years of age when including partially vaccinated patients.

Among patients over the age of 80, adjusted estimates tended towards a shorter LoS; however, these results were not statistically significant. There was no difference in the adjusted odds of in-hospital death between vaccinated and unvaccinated patients in any age group.

One notable observation, in this case, was fully vaccinated patients aged over the age of 80 having lower odds of in-hospital death when including all SARS-CoV-2 positive patients, regardless of the primary cause of hospitalization.

Implications

The study results suggest that COVID-19 patients vaccinated with an mRNA vaccine between the ages of 18–79 years in Norway had 43% lower odds of ICU admission and a shorter LoS in hospital than unvaccinated patients, with an average LoS reduction of 26% for fully vaccinated patients.

These results point to the fact that COVID-19 survivors had milder disease in vaccinated patients with a reduced need for hospital care and organ support. With vaccination coverage steadily increasing around the world, it would be extremely useful to conduct similar studies as this one for patient management and ongoing capacity planning in hospitals across the globe. Such studies also shed light on the overall efficacy of the vaccines that are designed to reduce disease severity and associated hospital stay.

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Written by

Sreetama Dutt

Sreetama Dutt has completed her B.Tech. in Biotechnology from SRM University in Chennai, India and holds an M.Sc. in Medical Microbiology from the University of Manchester, UK. Initially decided upon building her career in laboratory-based research, medical writing and communications happened to catch her when she least expected it. Of course, nothing is a coincidence.