MADISON, Wis. (AP) — Republican Sen. Ron Johnson, of Wisconsin, questioned the need for widespread COVID-19 vaccinations, saying in a radio interview “what do you care if your neighbor has one or not?”

Johnson, who has no medical expertise or background, made the comments Thursday during an interview with conservative talk radio host Vicki McKenna. Contrary to what medical experts advise, Johnson has said he doesn't need to be vaccinated because he had COVID-19 in the fall. On Thursday, he went further, questioning why anyone would get vaccinated or worry about why others have not.

“For the very young, I see no reason to be pushing vaccines on people.” Johnson said. “I certainly am going to vigorously resist any kind of government use or imposing of vaccine passports. ... That could be a very freedom-robbing step and people need to understand these things.”

Johnson's comments come as health officials in the U.S. and around the world urge people to get vaccinated for COVID-19 as soon as possible, saying that reaching herd immunity is the best shot at stopping the uncontrolled spread of the virus.

Herd immunity occurs when enough people have been vaccinated or have immunity from natural infection that the virus can’t easily spread and the pandemic fizzles out. Nobody knows for sure what the herd immunity threshold is for the coronavirus, but many experts say it’s 70% or higher. And the emergence of variants is further complicating the picture.

In Wisconsin, more than 41% of the population has received at least one shot of vaccine and roughly 30% has been fully vaccinated. But demand for vaccinations has slowed in parts of the U.S. in a worrisome sign.

Johnson, a former plastics manufacturer with a bachelor’s degree in business and accounting, said he doesn't think people should feel pressured to get vaccinated.

“The science tells us the vaccines are 95% effective, so if you have a vaccine quite honestly what do you care if your neighbor has one or not?” Johnson said. “What is it to you? You’ve got a vaccine and science is telling you it's very, very effective. So why is this big push to make sure everybody gets a vaccine? And it's to the point where you're going to shame people, you're going to force them to carry a card to prove that they've been vaccinated so they can still stay in society. I'm getting highly suspicious of what's happening here.”

The interview ended before Johnson explained what he was suspicious of.

On Friday, Johnson issued a statement doubling down on his earlier comments.

“Everyone should have the right to gather information, consult with their doctor and decide for themselves whether to get vaccinated,” Johnson said, noting his support for former President Donald Trump's Operation Warp Speed program to quickly develop a vaccine. “Now I believe government’s role (and therefore my role) is to help ensure transparency so that people have as much information as possible to make an informed decision for themselves.”

Johnson said it was legitimate to question whether people with a low risk of suffering a serious illness from COVID-19 should get vaccinated. He promised to “vigorously oppose” vaccine passports.

Republicans have portrayed vaccine passports as a heavy-handed intrusion into personal freedom and private health choices. They currently exist in only one state — a limited government partnership in New York with a private company — but that hasn’t stopped GOP lawmakers in a handful of states from rushing out legislative proposals to ban their use.

Johnson has not said yet whether he will seek a third term in 2022. A number of Democrats have already announced they are running, including Milwaukee Bucks executive Alex Lasry, state Treasurer Sarah Godlewski and Outagamie County Executive Tom Nelson.

Nelson tweeted that Johnson’s “scientifically illiterate beliefs are deadly and will only prolong the Covid crisis. Time for a new Senator.”

Godlewski also blasted Johnson, saying he “is literally campaigning against widespread vaccines. His denial of science isn’t just irresponsible, it’s downright dangerous, and Wisconsinites deserve so much better.”