MIAMI (NewsNation Now) — More than 5 million Americans have skipped out on their second dose of the COVID-19 vaccine, according to The Centers for Disease Control and Prevention.

“I was one of those people,” said Banoune Lapoint. “I took the first one in January, and I started to get an allergic reaction.”

Doctors say skipping the second dose is a troubling trend.

“If it is a concern about side effects, I would just remind people that these are mild and short term. Sore arm, headache, fatigue. It goes away quickly. Other people think the one dose is enough, and that is not the case. You need the second dose to have immunity,” said Dr. Preeti Malani of the University of Michigan.

Approximately 141 million, or about 43% of Americans, have received at least one dose of the vaccine so far and 29% of Americans have been fully vaccinated, according to the Centers for Disease Control and Prevention.

There has also been confusion about whether masks remain needed outdoors. Most scientific studies show the transmission of COVID-19 is very low outside. 

The CDC is expected to announce new guidelines regarding whether it’s necessary to wear a mask outside as early as Tuesday.