Covid Vaccines Greatly Reduced Severe Coronavirus Cases For Everyone Regardless Of Body Weight: Study In Lancet

The number of Covid-19 cases were greatly reduced among the vaccinated people. There was a significantly higher risk of severe disease at low and at high BMI compared with a healthy BMI.

Covid-19 vaccines greatly reduced the number of severe coronavirus cases for everyone regardless of their body weights, reports a new study published in the journal The Lancet Diabetes and Endocrinology. Vaccine effectiveness was observed to be similar for people with a higher body mass index (BMI) and a slightly healthy weight. However, vaccine effectiveness was slightly lower in the underweight group. The people belonging to this group were the least likely to have been vaccinated. 

A further analysis of vaccinated people who contracted Covid-19 was conducted. The analysis revealed that people of very low and very high BMI were more likely to experience severe disease than vaccinated healthy weight people. A previous analysis conducted before the vaccine rollout showed similar results.

People With BMI Over 40 Were Prioritised As A High-Risk Group

The United Kingdom vaccine rollout in 2021 prioritised people with a BMI of over 40 as a high-risk group. Early in the pandemic, obesity was pinpointed as a risk factor for severe Covid-19. Not much was known about the effectiveness of Covid-19 vaccines for people with obesity until now. 

According to previous research, people with obesity are less likely to take seasonal flu vaccines and have modestly reduced benefits from flu vaccinations. However, the exact reason behind this is not known. 

Study Provides Further Evidence That Covid-19 Vaccines Save Lives For People Of All Sizes

In a statement released by The Lancet, Dr Carmen Piernas, the lead author on the paper published in The Lancet Diabetes and Endocrinology journal, said the study findings provide further evidence that Covid-19 vaccines save lives for people of all sizes. The results provide reassurance to people with obesity that Covid-19 vaccines are equally as effective for them as for people with a lower BMI, and that vaccination substantially reduces their risk of severe illness if they are infected with Covid-19. 

Piernas added that the data also highlight the need for targeted efforts to increase vaccine uptake in people with a low BMI, where uptake is currently lower than for people with a higher BMI.

The health records of more than 12 million patients across 1,738 general practitioners in England taking part in QResearch, which is a secure database of healthcare information available to verified researchers, was analysed. As many as 91,71,524 patients out of those analysed were over 18 years old and had not previously been infected with SARS-CoV-2. 

People Divided Into Four Groups Based On BMI

Based on their BMI, the people were grouped according to four World Health Organization definitions for weight. A BMI of 18.5 to 24.9 kilograms per metre square means a healthy weight, one below 18.5 kilograms per metre square indicates underweight, a value of 25 to 29.9 kilograms per metre square indicates overweight, and a BMI of 30 and more represents obesity. The levels were adjusted for Asian people to reflect the higher health risks at lower BMI levels in the group. The researchers involved in the study accounted for characteristics such as age, sex, smoking status, and social deprivation in the analyses.

From December 8, 2020, Over 5.5 Lakh People Tested Positive For SARS-CoV-2

As many as 5,66,461 people tested positive for SARS-CoV-2 during the study from December 8, 2020 to November 17, 2021. The first vaccine was given in the UK on December 8, 2020. As many as 32,808 people were admitted to the hospital and 14,389 died.

Percentages Of People From The Four Groups Who Had Had No Covid-19 Vaccine

The researchers found that at the end of the study period, 23.3 per cent of the healthy weight group had had no doses of any Covid-19 vaccine. There were 35,09,231 people in the healthy weight group, and of these, 8,17,741 people had received no doses of Covid-19 vaccine. As many as 1,04,488 people out of 3,20,737 people in the underweight group, accounting for 32.6 per cent of the participants in that group, had not received any Covid-19 vaccine dose. Meanwhile, 5,13,570 people out of 30,62,925 people in the overweight group, and 3,22,890 people out of 22,78,649 people in the obese group had received no dose of Covid-19 vaccine. They accounted for 16.8 per cent and 14.2 per cent of the people in the overweight and obese groups respectively.

Vaccine Effectiveness Slightly Lower In Underweight People

The researchers compared the risk of severe disease in vaccinated people and non-vaccinated people at least 14 days after a second dose in order to understand vaccine effectiveness. The study found that vaccination provided high protection across all BMI groups. However, protection from vaccines was slightly lower in underweight people. 

Compared with underweight unvaccinated people, the vaccinated people with the same BMI had around half the likelihood of being hospitalised or dying. 

Vaccinated People Around 70 % Less Likely To Be Hospitalised Compared To Those Unvaccinated

Vaccinated people in the healthy and high BMI groups were around 70 per cent less likely to be hospitalised compared to unvaccinated people. The study found that people with a healthy or a higher BMI were around two-thirds less likely to die from Covid-19 than the unvaccinated people in the healthy or higher BMI groups two weeks after a second dose.

Covid-19 Cases Greatly Reduced Among Vaccinated People

The number of Covid-19 cases were greatly reduced among the vaccinated people. There was a significantly higher risk of severe disease at low and at high BMI compared with a healthy BMI, following two vaccine doses. For instance, a BMI of 17 was associated with a 50 per cent increase in risk of hospitalisation compared with a BMI of 23, the study reports. A very high BMI of 44 had three times the risk of hospitalisation compared with a healthy BMI.

Why People With Obesity Have Increased Risk Of Disease

Researchers do not know the cause behind increased risk of disease among people with obesity. People with a higher BMI also have a higher rate of seasonal flu infections. 

An altered immune response in heavier weight individuals may be responsible for the increased risk of severe disease among individuals with obesity, according to the authors. 

Limitations To The Study

Frailty or other conditions associated with low body weight may result in a reduced immune response, leading to reduced effectiveness of Covid-19 vaccines among people with a low BMI. 

The authors acknowledged certain limitations to the study, including the fact that some measurements of BMI were based on self-report, or on data recorded in General Practitioner records before the study onset that could be outdated. Since the number of people who had had three doses by the study close was limited, the effects of booster jobs could not be investigated. Also, the data was not enough for the researchers to investigate between Pfizer, AstraZeneca or Moderna vaccines, nor virus variants.