As you may know, the COVID-19 vaccine requires two separate shots: A first dose, and then a second dose four weeks after that one. Once you have both doses, you are officially vaccinated.

However, it turns out that many people are skipping their second doses of the vaccine. Nearly 8 percent, which is more than five million people, out of those who received the first dose of their Pfizer or Moderna vaccines, have missed their second doses, the Centers for Disease Control and Prevention (CDC) reports, and that number is steadily increasing as time goes by.

So what’s the reason so many people aren’t getting the second shot? Most people say that they’re scared of the side effects of the second dose, which is known to cause more severe symptoms than the first. You may experience anything such as fatigue, chills, fever, headache, swelling of the arm and more.

Additionally, other people say that they feel like they’re likely sufficiently vaccinated with just the initial dose of the vaccine. However, that isn’t true. While the first dose does partially vaccinate you, experts warn that to be 100% vaccinated, the second vaccine is, in fact, very needed to remain protected from the virus.

“I’m very worried, because you need that second dose,” said Dr. Paul Offit, a professor at the University of Pennsylvania and a member of the Food and Drug Administration’s vaccine advisory panel.

The only vaccine that is given as a single shot was Johnson & Johnson, which has since been put on hold after six women experienced rare blood clots after getting it. This has been the only vaccine that has been pulled so far.

A third reason for the second-dose skip is that some vaccine providers have canceled people’s second appointments after runnin out of supply or not having the correct brand in stock.

Health officials all over the country are taking measures to try and help people understand just thow important that second dose is. For example, in Arkansas and Illinois, first-dosers are now receiving reminders in the form of a all, text or letter. And in Pennsylvania, officials are attempting to make moves to help college students get their second dose once they’re not on campus anymore in the summer.

Some good news: Many people do still comply with getting their second dose—approximately 92 percent getting fully vaccinated.

If you’re getting vaccinated, don’t forget to get your second dose! With so many people skipping the second, it may take longer to get back to normal life.

Do you know anyone who’s willingly skipped out on the second doe of the vaccine?