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COVID vaccines work well for people of all body weights – but underweight and obesity remain risk factors for severe disease

Creator : Nerys M Astbury, Senior Researcher, Weight loss program and Weight problems, College of Oxford

Because the pandemic started, greater than 6 million folks have died from COVID world wide. The excellent news is that we now have a variety of remedies in addition to extremely efficient vaccines which have helped cut back the variety of extreme COVID instances.

Nonetheless, some folks usually tend to get very sick or die from COVID than others. Our analysis, carried out earlier than vaccines turned obtainable, confirmed that weight problems is likely one of the components that will increase an individual’s threat of being hospitalised or dying from COVID. We’ve now adopted this up with a brand new examine taking a look at how physique weight impacts the uptake and effectiveness of COVID vaccines, and found that being underweight can be a threat issue for extreme illness.

Weight problems is measured utilizing the physique mass index (BMI). That is calculated by dividing an individual’s weight in kilograms by their peak in meters, squared. An individual with a BMI under 18.5 is taken into account underweight, within the vary of 18.5–25 is taken into account wholesome weight, above 25 is taken into account to be chubby, and above 30 is taken into account overweight.

These early findings on the folks most in danger have been used to assist insurance policies that prioritised sure teams of individuals for vaccination. This included folks with a BMI of 40 or above.

Different analysis from earlier than the COVID pandemic has proven that folks with weight problems are much less doubtless to take up seasonal flu vaccines. There’s additionally proof to counsel that some vaccines work much less properly in folks with weight problems, though we don’t totally perceive the explanations for this.

What we did

In our new examine, printed in The Lancet Diabetes & Endocrinology, we used nameless well being data from greater than 9 million folks aged 18 and older in England. Our information coated the interval from December 8 2020 (the date the primary COVID vaccine was administered within the UK) till November 17 2021. Throughout this time, 566,461 folks out of the 9 million examined optimistic for COVID, of which 32,808 have been admitted to hospital and 14,389 died.

To analyze vaccine effectiveness throughout completely different physique weights, we seemed on the threat of extreme COVID outcomes (reminiscent of hospitalisation and dying) throughout the total BMI vary. Inside BMI teams, we in contrast individuals who have been vaccinated with folks of the identical age, intercourse and different traits who hadn’t been vaccinated.

We discovered COVID vaccines have been extremely efficient in opposition to extreme outcomes in all BMI classes, particularly after the second and third doses. After the second dose, vaccinated folks in wholesome weight, chubby or weight problems teams have been nearly 70% much less prone to be hospitalised because of COVID than their unvaccinated counterparts. Equally, vaccinated folks within the wholesome weight, chubby and weight problems teams have been round 60%–74% much less prone to die from COVID than unvaccinated folks with the identical BMI.




Learn extra:
COVID vaccines for kids below 5: what dad and mom have to know


Our outcomes point out that COVID vaccines could also be barely much less efficient in people who find themselves underweight. Vaccinated individuals who have been underweight have been round 50% much less prone to be hospitalised and round 40% much less prone to die than their unvaccinated counterparts. In fact, this nonetheless represents an excellent degree of safety.

Individuals who have been underweight have been additionally the least prone to get vaccinated within the first occasion, and this was true throughout all age teams. The proportion of totally vaccinated folks was highest amongst individuals who have been chubby and overweight. In our examine, totally vaccinated meant having obtained two or three doses, as not everybody was eligible but for a booster on the finish of our examine interval.

Uptake of vaccination by age and BMI

A chart showing the uptake of COVID vaccination by age group and BMI.

Tailored from The Lancet Diabetes & Endocrinology, Creator offered

We additionally seemed on the threat of extreme COVID outcomes solely among the many individuals who had been vaccinated with no less than one dose. Though vaccination massively lowered the chance of extreme COVID, individuals who have been underweight and people with weight problems remained at larger threat of hospitalisation or dying from COVID than folks of a wholesome weight. This was additionally the case earlier than vaccines have been rolled out.

Threat of COVID hospitalisation and dying after two vaccine doses by BMI

Two figures with curves showing the increasing risk of hospitalisation (left) and death (right) with increasing BMI, after two doses of COVID vaccine.

Tailored from The Lancet Diabetes & Endocrinology, Creator offered

The associations turned much less vital amongst those that had obtained a 3rd dose. However as solely a restricted variety of folks have been eligible for the third dose by the tip of the examine interval, we’ll want additional analysis to higher perceive the impact of boosters.

The information additionally didn’t enable us to discover any variations between the completely different COVID vaccines, or to evaluate the affect of various COVID variants.




Learn extra:
Irritation: the important thing issue that explains vulnerability to extreme COVID


Individuals who have two doses of a COVID vaccine obtain a excessive degree of safety in opposition to extreme outcomes, no matter their physique weight. Given the slight discount in vaccine effectiveness in people who find themselves underweight, focused efforts could also be wanted on this group to extend vaccine uptake.

Although extreme outcomes have been a lot rarer after vaccination, folks within the underweight and overweight teams have been at considerably greater threat in comparison with folks of a wholesome weight.

Public well being methods to assist folks obtain and keep a wholesome weight have many advantages. One vital one could also be to assist cut back the burden of extreme COVID.

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