WASHINGTON - The World Health Organization hopes to inoculate 5 million children in Yemen against polio this year, while in the United States a movement opposed to the use of vaccines in the very young is gaining momentum, prompting warnings from many doctors that this trend could result in dangerous outbreaks of diseases once under control.

Dr. Peter J. Hotez, an expert in infectious diseases and pediatric care, is among those physicians arguing strenuously against those who oppose vaccines, based on their beliefs that American vaccination practices are putting their children at risk.

FILE - Dr. Peter Hotez, dean of the Baylor College FILE - Dr. Peter Hotez, dean of the Baylor College of Tropical Medicine, shows Associated Press journalists areas of Houston's 5th Ward that may be at high risk for mosquitoes capable of transmitting the Zika virus in Houston. FILE - Dr. Peter Hotez, dean of the Baylor College of Tropical Medicine, shows Associated Press journalists areas of Houston's 5th Ward that may be at high risk for mosquitoes capable of transmitting the Zika virus in Houston.

Pitted against Hotez are groups such as Texans for Vaccine Choice, whose members generally believe that vaccines administered to children may be linked to the developmental disorder autism. The scientific establishment has repeatedly discredited such theories, but parents who oppose vaccines say they should be able to disregard their government’s advice and choose for themselves whether to vaccinate their children.

Vaccine opponents speak out

Texans for Vaccine Choice is a “very effective organization,” Hotez said.

Another group called Revolution for Truth plans a march on Washington in late March. On Facebook the group says its purpose is “to protest the ... media’s biased coverage and demonization of anyone who advocates for safer vaccines or defends the legal right to make informed, voluntary vaccine choices.”

The vaccine skeptics’ beliefs fly in the face of voluminous statistical evidence compiled by the U.S. government’s health agencies, WHO and many other groups. This year, however, their movement has been energized by some anti-vaccine comments President Donald Trump made years ago, and by his perceived opposition to vaccines during the political campaign that put him in the White House.

Vaccinations against childhood diseases such as measles, mumps and rubella are compulsory in most of the U.S., but Texas is one of the states that will hear appeals from parents who oppose the practice, and, in many cases, will exempt their children from vaccination requirements.

Emboldened by their successes in the appeals process — an estimated 50,000 Texas schoolchildren are no longer being inoculated — “vaccine choice” groups are now shifting their operations into politics, social media and other arenas to appeal to a broader sector of the public.

The Texas Health Services department reports that measles vaccination coverage in certain counties is close to dropping below 95 percent, the rate necessary to ensure widespread immunity and prevent measles outbreaks.

FILE - Michelle Moore poses for a photo with her t FILE - Michelle Moore poses for a photo with her twin daughters, Sierra (right) and Savannah in Lake Oswego, Oregon. Moore is among the vaccine skeptics who have been widely ridiculed since more than 100 people fell ill in a measles outbreak traced to Disneyland. FILE - Michelle Moore poses for a photo with her twin daughters, Sierra (right) and Savannah in Lake Oswego, Oregon. Moore is among the vaccine skeptics who have been widely ridiculed since more than 100 people fell ill in a measles outbreak traced to Disneyland.

Measles scares of 1960s could return

Hotez says he is greatly concerned by the implications of what is happening in Texas. He is a professor of pediatrics, molecular virology and microbiology at Baylor University in Texas, among other appointments, and also directs a center for vaccine development at Texas Children’s Hospital, in Houston. This gives him a broad overview of many issues involving the growth and development in young children.

In a Skype interview with VOA this week, Hotez said the increase in parental opposition to children’s vaccinations could lead to a deadly resurgence of measles in Texas and other parts of the country.

Measles epidemics that were a public-health problem in the United States in the mid-20th century have largely disappeared, thanks to vaccinations, Hofez and his allies say, or because of better sanitation and child-rearing practices, according to the skeptics.

In the 1970s, before children were widely vaccinated, measles was the leading cause of death of children worldwide.

“Measles is a bad actor,” Hofez said. “Even if it doesn’t kill, it can cause neurologic devastation,” he added, contrasting the potential of a full-scale outbreak with the popular notion that measles generally is a less-threatening disease — a rash, accompanied by fever, that goes away after a week or two.

Vaccines save 2.5 million lives annually

Public health experts estimate that vaccines prevent the deaths of about 2.5 million children throughout the world every year, but they say measles and whooping cough still circulate easily in populations where enough people are unvaccinated.

The World Health Organization credits vaccination practices worldwide with a 79 percent reduction in measles deaths, but the medical community also says the highly contagious nature of the measles virus makes the disease a continuing danger.

Hotez said he is concerned that the anti-vaccine movement in Texas and several other parts of the U.S. could become a political contagion nationwide.

Enter presidential candidate Donald Trump, who has linked vaccines to autism in public comments dating back to at least 2012. During a Republican candidates’ debate months before last year’s presidential election, Trump recounted a tale of one of his employees with a 2-year-old child who “went to have the vaccine and came back and a week later got a tremendous fever, got very, very sick, now is autistic.”

Personal connection to autism

Hotez is in a unique position to refute this, as both a vaccine scientist and the father of an adult daughter who has autism. He says there is absolutely no connection between the two. He said the neurologic development in the brain that leads to autism takes place in the first trimester of pregnancy, before any vaccines have been given.

FILE - Robert F. Kennedy Jr. enters the lobby of T FILE - Robert F. Kennedy Jr. enters the lobby of Trump Tower in Manhattan, New York, Jan. 10, 2017. FILE - Robert F. Kennedy Jr. enters the lobby of Trump Tower in Manhattan, New York, Jan. 10, 2017.

Before the U.S. election, Trump met with Robert F. Kennedy Jr., a member of a prominent family associated with the Democratic Party; Kennedy, who has no medical background, supports a controversial theory that vaccines are linked to autism, a developmental disorder that has been diagnosed with increasing frequency in recent decades.

Kennedy said he was invited to discuss vaccine safety with Trump before his inauguration, and that the president-elect asked him to head a commission on vaccine safety and scientific integrity. No formal announcement of such a commission has yet been issued.

Vaccine opponents date their movement to 1998, when British physician Anthony Wakefield published a study that proposed a link between vaccines, particularly those containing the preservative thimerasol, and autism (thimerasol is no long used by any vaccine makers).

Opposition rooted in fraud

A subsequent investigation showed that Wakefield’s research study was too small to produce any worthwhile conclusions, and that in fact it was conducted fraudulently. Wakefield lost his medical license, and the British medical journal Lancet formally retracted his article after discovering that Wakefield received financial support from people who were engaged in lawsuits against vaccine makers.

Scientists the world over have almost unanimously repudiated the vaccines-produce-autism theory as unsubstantiated, misleading and dangerous misinformation. Wakefield, who still calls himself a doctor despite the loss of his license to practice medicine, has since moved to Texas where he is active in the anti-vaccine movement.

Hotez wants to warn the public about the dangers of refusing vaccines. He told VOA that scientists, especially those in public health, have to get the message out that vaccines work, and that they have no harmful side effects.

In a previous report on the anti-vaccine movement, Dr. Anthony Fauci, an infectious disease expert at the National Institutes of Health, told VOA: “If you had to pick out one intervention, if you balance the investment that you make in the research and the implementation and the health benefits, vaccines have to be at either the top of the list or very much on the short list.”

Some fear government ‘conspiracies’

Hotez is concerned about pseudoscience and the anti-vaccination movement’s frequent claims of government conspiracies. If the influence of those who oppose vaccinations spreads further, he said, the health of large numbers of children could be threatened.

“We’re playing with fire here,” the scientist said. “These are deadly diseases. These are ones that we’ve been able to eliminate mostly in the United States, and I’m concerned that we’re going to return to a situation that we faced before 1963, when 50,000 children required hospitalization from measles every year and about 500 children died of measles. ... We could face that kind of situation in Texas if this trend continues.”

Hotez is also worried that the anti-vaccine movement could have global repercussions: “The U.S. is very good at exporting its culture. We export our Hollywood movies; we export our rock stars. We’re going to export what I’m calling vaccine hesitancy.

“We could start seeing this trend happening in some of the big middle-income countries, such as India and Nigeria, Brazil, China,” Hotez continued. “And this could even lead to a reversal of all the great gains that we’ve made. … I’m quite worried that we could see a turnaround for the worst.”

It could mean that countries around the world will have to continue spending money on vaccines for diseases that could be wiped out, such as polio and measles, because citizens in the richest part of the world decided not to inoculate their children, and that children the world over will die and suffer permanent disability because parents did not have them vaccinated.