Many individuals throughout the world proceed to debate whether the coronavirus disease 2019 (COVID-19) pandemic was deserving of the intensive and extensive efforts made by the federal government and personal sectors alike to develop population-wide vaccines and vaccination programs. A brand new study posted on the medRxiv* preprint server examines hospitalization and mortality rates from COVID-19 before and after the rollout of the vaccine in England.

Study: Estimating the effectiveness of COVID-19 vaccination against COVID-19 hospitalisation and death: a cohort study based on the 2021 Census, England. Image Credit: Looker Studio / Shutterstock.com

*Vital notice: medRxiv publishes preliminary scientific reports that aren’t peer-reviewed and, due to this fact, mustn’t be considered conclusive, guide clinical practice/health-related behavior, or treated as established information.

Concerning the study

Early in December 2020, the COVID-19 messenger ribonucleic acid (mRNA) vaccine from Pfizer/BioNTech was rolled out in the UK, followed by the Moderna mRNA and Oxford/AstraZeneca adenovirus vector vaccine ChAdOx1-S. Clinical trials on each of those vaccines showed high vaccine effectiveness (VE) in stopping symptomatic and severe COVID-19.

In the present study, researchers examine population-level data from the 2021 Census in England that, comprised over 580,000 individuals 16 years or older.

The information of people who had received one, two, or three doses of the vaccine were examined and stratified by the point since each dose. The first final result of this study was to evaluate the likelihood of hospitalization for vaccinated participants after each exposure and at different time points following each dose using unvaccinated participants as controls.

VE against hospitalization

One dose of the COVID-19 vaccine reduced the likelihood of hospitalization by 52%, whereas two doses increased VE to 56%.

VE against COVID-19 hospitalization was negative three or more months after the primary dose, regardless of age; nonetheless, it was highest in those between 30-64 years and 65-79 years of age after the second dose. Following the third booster dose, VE peaked within the 65-79 years age group at about 88%.

After three doses, the danger of hospitalization declined by almost 78%. The protection offered by a full primary course and third booster dose declined to about 68% at three or more months from the third dose. The best reduction in VE at this point was in those between 30-64 years of age.

VE against mortality

The danger of mortality declined by almost 60% after one vaccine dose. A notable exception is in those over the age of 80, who exhibited almost zero VE with one dose. Protection rose to 90% overall after the second dose; nonetheless, it remained lower in those over 80 years old as in comparison with the high VE in individuals aged 30-79 years.

The very best VE of 93% was observed after the booster dose; nonetheless, those between 16-29 years exhibited a VE of 71%. Furthermore, VE declined at three or more months from the second and third doses but remained high except within the 16-29 years age group, where it waned substantially.

VE by variant

Throughout the Omicron wave, the COVID-19 vaccine higher protected individuals against hospitalization than previous reports; nonetheless, VE against mortality declined.

Furthermore, VE against hospitalization was higher after the second dose than for either the primary or third dose through the Omicron wave. Nonetheless, VE declined at each three to 6 months and further reduced to about 40% over six months from the second dose.

After the third dose, protection against hospitalization declined from 80% before the onset of the Omicron wave to 55% thereafter. Nonetheless, the reduction of VE by 23% that was observed three months after the third dose pre-Omicron didn’t occur through the Omicron wave.  

Protection against COVID-19 mortality declined after the primary, second, and third vaccine doses through the Omicron-dominant period. In reality, the primary dose didn’t confer significant protection, whereas VE against mortality declined to about 50% over six months after the second dose.

VE by vaccine type

Overall, mRNA vaccines performed higher than other COVID-19 vaccines; nonetheless, the population protected in each case varied. The mRNA vaccines showed waning VE against hospitalization at three months or more from the booster dose, whereas each vaccine types exhibited waning VE against mortality three months or more following the second dose.  

Confounding aspects

Confounding aspects likely affected the calculation of VE against mortality on account of non-COVID-19 causes.

Some possible causes of error could possibly be the administration of vector-based vaccines to essentially the most frail and at-risk patients and the vaccination of healthy individuals with more practical vaccines. The follow-up on this study began in late March 2021, whereas the vaccination campaign began on December 8, 2022.

Thus, the oldest individuals on this study were likely frailer or lacked access to vaccination sites initially of the campaign. This affected their possibilities of developing severe or fatal COVID-19 after the primary dose.

Frailty biases likely explain the lower VE after the primary and second doses, as these were probably older and sicker people whose vaccination was delayed on account of health concerns.

Similarly, younger and healthy persons are likelier to have received the booster doses later. In consequence, the three to 6 and over six-month follow-up after the booster dose will probably be biased towards high-risk individuals. These findings indicate that health status is a big confounding factor after adjusting for other aspects.

Given the inconsistency of the decrease across the breakdowns, we cannot say there is robust evidence of waning protection against COVID-19 hospitalisation. For VE against COVID-19 mortality, we do see consistent decreases across the varied breakdowns. This might indicate waning of protection.”

What are the implications?

The vaccine effectiveness estimates show increased protection with variety of doses and a high level of protection against each COVID-19 hospitalisation and mortality for the third/booster dose.”

For the primary time, the present study adjusted for socioeconomic and health status variables using data from the 2021 Census, thereby improving the accuracy of real-world VE estimation. Nevertheless, residual confounding by health status is observable, which needs to be factored into any VE estimation tool in future studies.

*Vital notice: medRxiv publishes preliminary scientific reports that aren’t peer-reviewed and, due to this fact, mustn’t be considered conclusive, guide clinical practice/health-related behavior, or treated as established information.