Students at Cor de Maria school in Olot (Girona), where the stricken child is enrolled. PERE DURAN / EL PAÍS

The parents of the six-year-old boy who became the first person to contract diphtheria in Spain since 1987 said they feel “tricked” by the anti-vaccination groups they once admired.

“The family is devastated and admit that they feel tricked, because they were not properly informed,” said Catalan public health chief Antoni Mateu. “They have a deep sense of guilt, which we are trying to rid them of.”

The child remains in critical condition in the intensive care unit of Vall d’Hebron hospital in Barcelona.

The child’s parents have now agreed to let their younger daughter get her shots

The health department said that the patient was responding well to the treatment – an anti-toxin that had to be urgently imported from Russia and France as it had not been prescribed in Spain for three decades. Madrid issued an international call for help, and the Russian ambassador to Spain managed to get the first dose flown in from Moscow earlier this week.

“The anti-toxin is doing its job, and we see that in the way things are getting resolved, but we cannot predict how it will progress,” warned Mateu.

The health official rejected the possibility of charging the parents for the treatment their son is receiving.

“In no way are we considering that option. There are two victims here: the child and the parents,” said Mateu.

An investigation is underway to find the original carrier of the bacterium that latched on to the child’s body, but Mateu warned that it would “be difficult to find him, especially if he is asymptomatic.”

Everyone who was in touch with the child in the days prior to his hospital admission is under surveillance for signs of the disease. Classmates at Cor de Maria school, in the town of Olot, had their health records checked for vaccinations. All of them have been taking preventive medication and receiving additional immunizations, health officials said.

There are two victims here: the child and the parents”

Antoni Mateu, Catalan public health chief

The child’s parents have agreed to let their younger daughter get her shots, Mateu added.

The first symptoms showed up on May 23, but it was not until May 28 that the little boy was admitted to the local hospital. That same day, the national public health agency received an alert that this might be a case of diphtheria.

On Friday, May 29, the National Microbiology Center received the sample, and the diagnosis was confirmed the following day. The minor was transferred to Vall d’Hebron and the Health Ministry began the worldwide search for the anti-toxin required to save his life.

Diphtheria vaccination rates in Spain are between 90 and 95 percent following systematic public health campaigns that began in 1945. Thanks to these efforts, the dangerous disease had been eradicated in the country.