Gov. Charlie Baker has expanded eligibility for COVID-19 vaccines to people with a Body Mass Index, or BMI, of 25 or above, in line with standards set by the Centers for Disease Control and Prevention. Previously, only those with a BMI over 30, who qualify as medically obese, were eligibile based on weight.

In an interview with GBH All Things Considered host Arun Rath, Dr. Rachael Piltch-Loeb of Harvard's T.H. Chan School of Public Health discussed the rationale behind the change.

"Several studies that have been done in terms of the risk factors for severe COVID — things like hospitalizations or needing to be hooked up to a ventilator when hospitalized, [and] increased risk for mortality, as well — have shown that those who are overweight are also at increased risk, not just those who are obese," Piltch-Loeb said.

Some argue that BMI reduces wellbeing to a number or a size rather than giving a full picture of a person's overall health — something that Piltch-Loeb acknowleged.

"I think that those criticisms can be valid," she said. "There are pieces of evidence that have shown that BMI is an indicator of a worse experience. And so that's where the CDC recommendations are coming from, and that's where the state is making their judgment call at this point in time."

Piltch-Loeb said that with more people getting vaccinated, expanding eligibilty is a sound policy, especially with new COVID-19 variants circulating.

"We want to have an immune response in as many people as possible before the variants get to those people and can infect them," she said. "And so the more people who are vaccinated, the less opportunity that variants have to infect more individuals."