A second US child with measles has died as Texas grapples with an outbreak of the childhood disease that has resulted in nearly 500 cases and spread across 22 states.

The school-aged child, who was unvaccinated and had no underlying health conditions, died on Thursday (local time) in the hospital from measles pulmonary failure, the Texas Department of State Health Services said.

“The child was receiving treatment for complications of measles while hospitalised,” Aaron Davis, a spokesperson for UMC Health System in Lubbock, Texas, said in an email.

It is the second death of a child in Texas since the measles outbreak began in late January.

Health and Human Services Secretary Robert F Kennedy Jr in a post on X, identified the child as eight-year-old Daisy Hildebrand.

Kennedy, a noted anti-vaccine advocate who has previously has said vaccination is a personal choice, said on Sunday vaccines were the best protection against measles.

“The most effective way to prevent the spread of measles is the MMR vaccine,” he said in the post on X.

There were 642 confirmed cases of measles, 499 of those in Texas, he said.

Kennedy visited Texas to comfort the Hildebrand family after their daughter’s death.

He said he got to know the family of the first child in Texas to die in the measles outbreak, Kayley Fehr, “after she passed away in February”.

Kennedy said that teams from the US Centres for Disease Control and Prevention had been sent to Texas at the request of the state’s governor, Greg Abbott.

Kennedy has previously recommended vitamin A as a measles treatment, along with good nutrition. While vitamin A has been shown in some studies in developing countries to lessen the severity of symptoms, it can lead to liver toxicity in high quantities.

Kennedy’s post about vaccines came after Republican US Senator Bill Cassidy, who is also a physician and chair of the Senate health committee, wrote on X after the child’s death was disclosed: “Everyone should be vaccinated”.

“Top health officials should say so unequivocally b/4 another child dies,” Cassidy wrote on X.

Cassidy backed Kennedy’s confirmation as the US health boss after Kennedy promised not to make changes to vaccine oversight.

The measles vaccine is 97 per cent effective after two shots.

On its website, the US Centres for Disease Control and Prevention says the vaccine is “the best protection against measles”, which spreads through the air when an infected person sneezes or coughs.

-AAP