BCG is ineffective when applied to adults, according to a Fiocruz study

A study carried out by researchers from the Oswaldo Cruz Foundation (Fiocruz) reinforces that the BCG vaccine should be applied to children up to 5 years of age, to prevent the severe form of tuberculosis, but it is ineffective when applied to adults against the initial infection by the virus Mycobacterium tuberculosiswhich causes the disease.

Published this week in the British magazine The Lancet – Infectious Diseases, the work also indicates the need to develop new vaccines against the disease across the world.

The work was carried out only in Brazil, in the cities of Campo Grande (MS), Manaus (AM) and Rio de Janeiro (RJ) by researchers Julio Croda, Margareth Dalcolmo and Marcus Lacerda. The survey is part of the Brace clinical trial, with randomized BCG, in which participants were chosen at random, whose main objective was to evaluate the effectiveness of the vaccine in healthcare workers against Covid-19.

The Brace study was funded by the Bill and Melinda Gates Foundation and covered five countries: Brazil, the Netherlands, Spain, Australia and the United Kingdom.

Protection

A Brazil Agencyresearcher Julio Croda explained that the concern was to evaluate whether BCG revaccination would protect health workers from tuberculosis infections.

“The previous article showed that, eventually, revaccination with BCG could protect against tuberculosis infection and we went to test this hypothesis”. The conclusion was that revaccination in adults is not recommended.

“We showed that, in Brazil, revaccination with BCG does not protect against Mycobacterium tuberculosis”, he stated. Two groups of health professionals were chosen, totaling 2 thousand people, of which one thousand were revaccinated with BCG and one thousand did not receive the vaccine. Blood tests were done before the person was vaccinated with BCG and after 12 months, to see how many patients acquired this infection. It was then observed that the chance of becoming infected, around 3%, was the same in both groups.

“Those who received the vaccine had the same chance of infection as those who were not vaccinated”, reported Julio Croda. According to Croda, in Brazil there is no recommendation for revaccination. The study proves that the recommendation not to revaccinate remains appropriate, because it does not guarantee protection for those who took the vaccine.

South Africa

A similar study is being carried out in South Africa to try to revalidate initial work that indicated that, eventually, revaccinating the population could guarantee protection.

“In Brazil, this conclusion was not reached,” said Croda. According to him, there is no recommendation for revaccination of adults with BCG in any country. More studies are needed to evaluate the initial finding which, if proven, could lead to the creation of a different public policy, with the possibility of revaccination of adults.

The data evaluated in the three Brazilian cities shows that there is no specific indication for vaccinating groups at risk for acquiring tuberculosis, such as health workers. By extension, there is also no guidance for revaccination of the Brazilian adult population.

Vaccines

For the researcher, the study makes it clear that Brazil needs new vaccines against tuberculosis, because BCG, which is given when the child is born, only protects against severe forms up to 5 years of age.

For populations that are at risk of the disease, he advocated for more investment in the development of new vaccines. This is the goal of the World Health Organization (WHO), which is financing a study in Africa, where there are many cases of tuberculosis.

“It is important that we have other vaccines in development, including in Brazil, that can be applied to risk groups and can prevent the disease itself, tuberculosis.” There is still no vaccine in the world against this disease.

Fiocruz

Fiocruz is in the initial phase of research into a new vaccine against tuberculosis. Clinical tests have not yet been carried out.

“We demonstrated that the BCG vaccine is good for children, to prevent severe forms. But there is still a need for a more effective vaccine for the active disease and, especially for risk groups, such as health professionals, populations deprived of liberty, indigenous people, people with HIV/AIDS. In Brazil, Croda said that tuberculosis is the main cause of death related to infectious diseases, after covid-19.

The director of the Brazilian Society of Immunizations (SBIm), Isabela Balladai, highlighted that the Fiocruz study validates everything that is already known.

“BCG does not protect against pulmonary tuberculosis. It protects against serious forms, such as tuberculous meningitis and miliary tuberculosis. Two serious forms that occurred in childhood, in the first months of the baby’s life. Therefore, we vaccinate children early at birth. Since there was high coverage with BCG, rare cases of these two severe forms have been seen in immunocompromised people”, said the specialist.

The doctor recalled that the Ministry of Health even recommended booster immunization with BCG at 10 years of age, but this was discarded in 2019. “The booster was withdrawn because, in addition to causing a more intense local adverse event, as it was a second dose, It didn’t protect either.

The Fiocruz study validates that BCG is a vaccine for children up to 5 years of age and that it should be administered as early as possible after birth. Ideally still”, said Isabela Balladai.

*With information from Agência Brasil

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