Only about 40.3% of eligible Americans have received a COVID-19 vaccine booster shot, according to CDC data, despite public health officials agreeing that the extra dose is the best defense against severe outcomes as the highly-transmissible Omicron version of the coronavirus circulates.

Doctors told Yahoo Finance that three primary factors are contributing to the booster drive’s struggles: confusing messaging from public health officials, misconceptions about the severity of the Omicron variant, and increased political polarization related to the pandemic.

“Much of the issue comes down to clarity of messaging,” Dr. Anand Swaminathan, a New Jersey-based emergency medicine physician, told Yahoo Finance. “We need to be crystal clear about what vaccines are intended to do, the fact they don’t work on an individual level but on a population level, and why and when boosters are recommended and for whom.”

Booster is part of larger vaccine confusion

Initially, some health officials argued against getting boosted right away, with reasons ranging from vaccine equity to necessity at the time.

But guidance has changed, and it’s now recommended that anyone eligible for a booster get one as soon as possible.

“That is the nature of science — as we learn more, we tailor our recommendations based on the best data available at that time,” Dr. Shikha Jain, assistant professor of medicine at the University of Illinois at Chicago, told Yahoo Finance. “However, the messaging to the public has not been as smooth, and I feel many are confused as to when they would be eligible for a booster.”

Relatedly, there is still a lack of understanding of what vaccines actually are meant to achieve.

Both Jain and Swaminathan stressed that the ultimate goal is not to actually prevent infection but to significantly protect against serious disease, hospitalization, and death.