A review of 58 different changes to labels on vaccines made between 1996 and 2015 has shown very few dangers in vaccination, and changes that were made were mostly to ensure people vulnerable to side effects or allergies were protected, they found.

"These data highlight the robustness of the vaccine approval and postmarketing surveillance processes and confirm population vaccination as a major public health strategy," the team at Tel Aviv Sourasky Medical Center wrote in their report, published in the Annals of Internal Medicine.

Vaccine experts worry about a small but vocal group of vaccine skeptics who have cast doubt on the safety of vaccines, which go through a rigorous process of testing before they are approved by the US Food and Drug Administration and other global drug regulators.

The anti-vaxxer movement

The director of the National Institutes of Health, Dr. Francis Collins, said he's worried about some Americans' skepticism of vaccines and said it could affect the people's acceptance of the vaccine.

The first phase III trial of a possible coronavirus vaccine started in the Unites States on Monday, and Collins stressed that while development went quickly, the NIH was not cutting corners on safety.

"One of the things I'm worried about is there's a lot of skepticism in America about the vaccine and something like 25% of people say I'm not sure I would take that vaccine," Collins told CNN's Wolf Blitzer earlier this month.

It's important, Collins said, for everyone to get the vaccine when it's available. "It'll be really critical to do that if we're going to develop the level of herd immunity across the country so that this doesn't come roaring back the next time, the next fall, the next summer. We won't know," he said.

Asked if he worried about the anti-vaxxer movement, Dr. Anthony Fauci said, "I do."

"We have to admit and realize that there is an anti-vax movement that we've had to struggle with in this country," said Fauci, director of the National Institute of Allergy and Infectious Diseases, speaking earlier this month on the PBS Newshour.

"I believe the solution to that would be community engagement and community outreach -- to get people that are trusted by the community to go out there and explain to them the importance of not only getting engaged in the vaccine trial, but the importance of, when the vaccine has been shown to be safe and effective to actually take the vaccine."

It could be life-saving, he said, "and it certainly would be the solution to this terrible pandemic."

Fauci said he is "cautiously optimistic" that the country will have a vaccine by the end of 2020 or the start of 2021. "When you're dealing with vaccines, you can't guarantee things," he said.

"I feel optimistic -- nobody guarantees it but I feel optimistic -- that we will have a vaccine, one or more, that we can start distributing to people," Fauci added.

Post-market vaccine monitoring

Once approved and released for public use, the