SIOUX FALLS, S.D. — E-cigarettes are often portrayed as safer than cigarettes. But a new study indicates the use of e-cigarettes, or vaping, makes it harder to fight infections — whether or not the e-cigarette contains nicotine.

Vaping weakens cells in the body that are crucial to the fight against infections, according to the laboratory study by researchers at Veterans Affairs San Diego Healthcare System and the University of California San Diego, published earlier this month in the American Journal of Physiology-Cell Physiology.

The negative effect on the cells known as neutrophils, a type of white blood cell, was similar to that experienced when they are exposed to environmental toxins such as cigarette smoke, the researchers found in the study conducted on both humans and mice.

The study adds to the body of research showing that vaping's reputation as a safer alternative to smoking may be less true than many believe. Based on the findings, Dr. Laura E. Crotty Alexander of VA San Diego and University of California San Diego and the corresponding author on the paper, cautioned against using e-cigarettes.

“We recommend that vaping be avoided in general, as our data and other findings demonstrate multiple possible adverse health effects caused by the use of e-cigarette and vaping devices," she said.

The research was conducted by exposing human neutrophil cells to e-cigarette vapor, a practice later confirmed on mice. It shows vaping limited neutrophils ability to get to the site of an infection, fight it once they arrived and produce compounds that fight bacteria.

Crotty Alexander said that based on the lab findings, it appears that “the key chemicals that immune cells are exposed to during vaping cause dysfunction and thus weaken the immune system.”

Further work by the researchers will focus on how the amount or style of vaping affects the immune system.

About 3% of American adults, approximately 7 million people, use e-cigarettes, according to a 2017 study. But youth and young adults are taking up the practice at a much higher rate, according to a 2016 U.S. Surgeon General report.

The emergence last year of a vaping related respiratory illness that sickened thousands and killed dozens drew a harsh spotlight to the potential risks of vaping.

Federal and state officials continue to investigate the illness, tentatively linked to the inclusion of vitamin E acetate within some e-cigarette fluids. Partly in response to the wave of illnesses, the Trump administration banned a range of vape liquid flavors and speedily approved legislation that raised the age of those allowed to buy both tobacco and vaping products that contain nicotine from 18 to 21.