The head of an international vaccine group says that misunderstandings and false information about vaccines are spreading on the internet and should be stopped.

　　Seth Berkley of Gavi, the Vaccine Alliance, spoke Tuesday to a gathering in Geneva, Switzerland, where the World Health Organization is meeting. Berkley said that false information "kills people." He noted strong scientific evidence of the safety of vaccines.

　　But, he said social media algorithms favor misinformation over facts. He added that such misinformation easily influences people who have not had a family member die from a preventable disease.

　　Berkley said people must consider the belief in misinformation as a contagious sickness.

　　He added, "This is a disease.This spreads at the speed of light, literally."

　　The World Health Organization says not enough people are getting the vaccine that prevents measles. It says this is why the disease is spreading around the world.

　　The organization says vaccines save two million lives every year.

　　Measles infections have risen sharply in countries that earlier had few cases, including the United States.

　　Seth Berkley argues that misinformation about vaccines is not a freedom of speech issue. He said Tuesday that social media companies should remove such content from their websites.

　　Alex Azar is Secretary of the U.S. Department of Health and Human Services. He made similar comments in his speech to the yearly meeting of the WHO. He said in the U.S., social media conspiracy groups confuse parents so they avoid getting needed vaccinations.

　　The American official also spoke of U.S. efforts to strengthen immunization programs around the world. He said, "Just recently, the U.S. supported a mass measles vaccination campaign in Nigeria that reached almost 10 million kids. We assisted with a diphtheria outbreak among Rohingya refugees in Bangladesh."

　　And he noted U.S. support of recent research about the yellow fever vaccine.

　　Azar has rejected criticism of comments about vaccines made by U.S. president Donald Trump before he became president. Trump posted on Twitter that vaccination could cause autism, a developmental disorder.

　　"A study says @Autism is out of control – a 78% increase in 10 years. Stop giving monstrous combined vaccinations."

　　Azar said that Trump was "extremely firm" in support of vaccinations.

　　Canada's Chief Public Health Officer Theresa Tam also spoke to the WHO delegates. She said health officials needed to do more about online misinformation. She said she was working on the issue with Twitter, Facebook, Google and other companies.

　　I'm Jonathan Evans.

　　Tom Miles wrote this story for Reuters news agency. Alice Bryant adapted it for Learning English.