(Bloomberg) -- People who are underweight or obese are most at risk of severe Covid, but a UK study found that two doses of vaccine still protect both groups well.

The researchers, who focused on patients at the two extremes of the body mass index scale, found that the shots worked slightly better for those at the high end of the measure in a study published in medical journal The Lancet Diabetes & Endocrinology on Friday. 

The scientists used health records of more than 9 million patients from generalist practices in England taking part in the database QResearch. 

“Our findings provide further evidence that Covid-19 vaccines save lives for people of all sizes,” said Carmen Piernas, the study’s lead author and a lecturer at the University of Oxford’s Nuffield Department of Primary Care Health Sciences.

Even so, the researchers found that people with extreme BMIs were at higher risk of severe disease than others with a healthy BMI. 

The data also highlight the need to increase vaccine uptake in people who are underweight, a category that’s less immunized, according to Piernas.  

©2022 Bloomberg L.P.