NEW YORK (CBSNewYork) — As COVID-19 vaccines become widely available and anyone 16 and older can now get one, there is also a number of issues that are slowing their uptake.

There is vaccine hesitancy for the second shot or at all, the Johnson & Johnson restart, rare side effects, and even shipping vaccines abroad, CBS2’s Dr. Max Gomez reported Monday.

READ MORECOVID Impact: New Poll Finds Vaccine Hesitancy Ticking Down, But Many Remain Opposed

Ironically, just as vaccine supplies have become ample, some cities and states are finding it harder and harder to administer coronavirus shots. That’s because hesitancy is becoming the latest challenge as the number of people who want to get vaccinated can do so, leaving only those who are reluctant to get the shots.

“We don’t need to have every American vaccinated, but we do need to have most and I hope most Americans decide this is really a safe and effective vaccine that is good for them and is good for their families,” said Dr. Ashish Jha, dean of the Brown University School of Public Health.

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A new CBS News poll shows more than 1 in 5 Americans, or 22%, say they will not get the vaccine. Another 18% are still unsure.

And about half of Republicans surveyed say they are either unsure or will not get the shot.

The message lost on those holdouts is that it’s that very vaccine that will make it safe to reopen schools, businesses, the entire economy.

“Don’t listen to politicians. Don’t listen to senators. Don’t listen to me. Talk to the people in your life who you trust,” said Andy Slavitt, senior advisor for the White House’s COVID response team.

READ MORENew York To ‘Immediately’ Resume Administering Johnson & Johnson COVID Vaccine After Federal Health Officials Lift Pause

Then there is the 8% of people who got their first shot of Moderna or Pfizer but have missed their second dose, either out of fear of side effects or a mistaken belief that one shot provides enough protection.

“It is critical that everybody get their second shot because that’s the only way we know that it is going to protect you for any extended period of time,” Jha said.

More states are resuming using the one-shot Johnson & Johnson vaccine this week, but with added warnings after very rare cases of blood clots. The U.S. will begin sharing its full inventory of millions of AstraZeneca vaccine doses with countries around the world.

Dr. Max Gomez