Reports about the return of preventable diseases have been spreading almost as fast as the outbreaks themselves, which are often linked to unvaccinated communities.

The Centers for Disease Control and Prevention confirmed 228 individual cases of measles in 12 states from Jan. 1 to March 7. As recently as 2016, there were 86 such cases nationwide for the whole year. In 2000, the illness was declared eliminated in the U.S.

Mumps and pertussis – whooping cough – have also been on the rise in recent years, the CDC said.

The newly revealed story of an Oregon boy who contracted tetanus after lacerating his head playing in a farm drew widespread interest not only because the unvaccinated child went through a horrendous ordeal that cost more than $800,000 in treatment, but because his parents declined a follow-up injection that would have kept him safe.

Last week, Ohio high school senior Ethan Lindenberger, who defied his mother’s objections and got vaccinated once he turned 18, told a Senate committee that it’s critical to combat mistaken claims about immunizations on social media.

The dissemination of misinformation about vaccines has become such an issue that Facebook and other social media sites have committed to making policy changes to counter the hoaxes.

“There are a lot of conspiracy theorists out there convincing people these things aren’t going to work, or that they’re going to hurt their children, or that the disease isn’t important,’’ said Yvonne Maldonado, chief of the division of Pediatric Infectious Diseases at Stanford University. “It’s easier to get that information out now than what it was before we had social media.’’

Here are some common myths about vaccines and the facts that refute them:

Myth 1: Vaccines are linked to autism

This is likely the most pervasive and pernicious myth, mostly stemming from a repeatedly debunked 1998 research paper authored by former British physician Andrew Wakefield and 12 colleagues, most of whom later retracted the conclusion.

The paper claimed there was a connection between the measles, mumps and rubella vaccine and autism, a notion most recently refuted yet again by a large-scale study of more than 650,000 children in Denmark published this month.

“Scientists in the United States and other countries have carefully studied the MMR shot,’’ the CDC website says. “None has found a link between autism and the MMR shot.’’

Myth 2: Vaccines are toxic

The three chemicals that have raised concerns related to vaccines are mercury, aluminum and formaldehyde.

The CDC says the amount of potentially toxic ingredients in vaccines is minimal, pointing out breast milk has some mercury, but not enough to be harmful, and that the same goes for vaccines.

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“Components of vaccines are all there for a reason,’’ the CDC says. “Some (like aluminum) help the vaccine work better. Others (like formaldehyde) were used during manufacturing and have been removed except for a tiny trace.’’

Myth 3: Those diseases have been wiped out

Maldonado believes that in some ways vaccines have become victims of their own success, in that many people erroneously believe diseases like measles, mumps, tetanus, diphtheria and polio no longer exist.

When she was a practicing physician years ago, Maldonado said every week she would see children with serious and sometimes fatal illnesses, and she would yearn for immunizations to prevent them.

“And now we have these vaccines, so the families and the providers don’t see these diseases,’’ she said. “They don’t see these infections that kill children or leave them with neurological or other complications for the rest of their lives, so they think, ‘Why should I give my child an injection for something that isn’t around anymore?’’’

With less vaccination, those ailments stand a better chance of recurring.

Myth 4: Vaccines have serious side effects

Some side effects are indeed possible, most common among them light fever and pain and swelling in the injected area. But research has shown vaccines to be extremely safe. The FDA puts them through rigorous tests, monitors them and requires makers of new vaccines to show they won’t counteract those that are part of the regular schedule.

In the rare instances when the recipient of a vaccine develops an allergic reaction, the symptoms can be treated with a visit to the family doctor.

Myth 5: The flu shot will give you the flu

That common misperception probably stems from the vaccine usually getting administered at a time when colds are proliferating, so it’s easy to catch one and jump to the conclusion it was a result of the flu shot, which takes two weeks to take effect.

But the viruses contained in the flu shot are dead, so they can’t cause disease.

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The effectiveness of the flu shot varies by season, and the CDC estimated it prevented infection at only a 47 percent rate this season, although the figure rose to 61 percent for children up to 17. Still, getting a flu shot helps decrease the chances of hospitalization among those infected.

Last year, 80 percent of the children who died from the flu were not vaccinated.

Myth 6: Vaccines are not that effective

It’s true that no vaccine is completely foolproof, but some are as much as 99 percent effective. Vaccines are the main reason small pox has been eradicated from the U.S. and other contagious diseases have become rare.

Beyond that, those who can’t be vaccinated for medical reasons benefit from what’s known as “herd immunity,’’ meaning that if the vast majority of the population around them is immune, their chances of getting infected diminish greatly.

The CDC says for most contagious diseases, vaccination rates need to be between 80-95 percent for the entire “herd’’ to be protected.

Myth 7: The Internet’s the best guide

There’s obviously a wealth of valuable information online, and it could indeed enlighten those making decisions about the pros and cons of vaccines. But Maldonado warns the web is also rife with misinformation, pointing to a 2018 study that showed bots and Russian trolls have sought to foster discord about vaccines on Twitter.

She also notes the echo-chamber effect created by those seeking opinions that agree with their own.

“Facts and science don’t change people’s minds anymore,’’ Maldonado said. “People have emotional or psychological reasons for the decisions they make, and the facts they look at generally tend to support their view no matter what the facts are.’’

Maldonado said the best way to address questions or concerns about vaccines is through one-on-one interaction with a health care provider, often a pediatrician.