MIAMI (AFP) - Joe Accurso, a 47-year-old chiropractor, refused to vaccinate his daughter against polio, measles or whooping cough because he believes that getting sick wouldn't be dangerous and might even be good for her.
"I am actually disappointed that she doesn't have the opportunity to get the chicken pox, to get diseases that make her body stronger in the future. That is our big reason," he told Agence France-Presse.
Don't call them "anti-vaxxers". Joe and his wife Cathy, a physical therapist, see themselves as part of a vocal minority that believes in "vaccine choice". These parents - many of whom are white, educated and upper middle class - choose not to immunise their children against diseases which collectively used to kill millions children per year around the world.
They say these illnesses aren't so bad, compared to vaccines, the risks of which they believe are being withheld from the public in the name of pharmaceutical profits - a belief now shared by millions of people across the developed world, from the United States to Europe and Australia.
They are also swayed by purported medical whistleblowers who claim that vaccine effectiveness data has been skewed, that vaccine injuries are on the rise, and that dubious ingredients have been concealed.
Fuelled by distrust of the medical establishment, more than seven million people follow various US-based Facebook pages that question vaccines, wrote Richard Stein, a New York University cardiologist, last month in the journal Germs.
"Conspiracy theories on social media are alive and thriving, rejoicing their golden age," Stein said.
RESURGENCE OF MEASLES
Endemic measles was eradicated from the United States in 2000, and nationwide only about two per cent of kindergarteners have gone unvaccinated in recent years, according to the US Centers for Disease Control and Prevention (CDC).
But the danger comes when large pockets of people do not vaccinate and an area loses "herd immunity". In Minnesota, for example, child vaccination rates for measles, mumps and rubella (MMR) in the Somali-American community plummeted to 42 per cent in 2014, down from 92 per cent in 2004.
The result: 65 cases of measles in 2017, most of them unvaccinated Somali children - the largest single outbreak in a year that saw 120 cases nationwide, the CDC said.
Fears about autism spread after British anti-vaccine activist Andrew Wakefield - whose 1998 research alleging that vaccines trigger autism was found to be fraudulent - spoke to local Somali community groups in 2010 and 2011.
"One of the pseudoscience phony central tenets of the anti-vax movement is to claim that measles is a benign illness or even good for you," Peter Hotez, director of the Texas Children's Hospital Center for Vaccine Development, told AFP.
Such ideas are "deliberately misleading and false", and have real-world consequences, he added.
Measles can cause hearing loss, blindness, brain swelling and pneumonia. The CDC says that for every 1,000 children infected, one or two will die.
In the United States, recent measles outbreaks include one in Ohio's Amish community in 2014 (383 cases), and a nationwide 2015 outbreak that infected 188 and is believed to have started with a visitor to California's Disneyland amusement park.
A vaccinated elderly woman was the sole measles fatality that year.
INFLUENCE OF SOCIAL MEDIA
Social media may be perpetuating the anti-vaccine movement, said Naomi Smith, an Australian researcher.
Smith just completed a three-year study on how Facebook appears to have created a "filter bubble" around the fraught issue - so vaccine sceptics see their ideas reinforced on pages they follow.
When it comes to convincing hesitant parents to vaccinate their kids, Smith said both sides are at "a total impasse". People who hold strong anti-vaccination beliefs tend to believe personal testimonies, and "use a different standard of evidence than what the medical community uses," she told AFP.
To bridge the divide, some doctors, like Arizona pediatrician Tim Jacks, occasionally share their own personal stories with vaccine-hesitant parents.
In 2015, Jacks' daughter Maggie was battling leukemia, had recently finished a round of chemotherapy, and was exposed to measles while getting blood drawn at a Phoenix clinic.
Also exposed was his younger son, Eli, just 10 months old then and too young for the MMR shot.
The experience was scary, and required the family to spend two weeks in quarantine. Fortunately neither child fell ill, and Maggie, now six, is in remission from her cancer.
"We don't live in bubbles. So even going to the store and getting groceries, going to church, going to the park, you are interacting with other people and you are potentially exposing other people," Jacks said.
"Who is really at risk? It is the family that has a newborn that has no protection. It is the grandmas."
For Hotez, solutions include more engagement from scientists and laws that eliminate the personal choice to vaccinate, as now exist in 18 states.
After the Disneyland outbreak, California changed its laws to allow only medical exemptions for children who attend school, and vaccinations climbed.
"It is no longer simply a small cult," said Hotez.
"This is a well-organized movement that needs to be taken on directly."