Way immune system responds to tuberculosis vaccine varies among people

At the same time, there are also opportunities to improve the response to vaccines. For example, by vaccinating at a more optimal time. Follow-up research must show at what time that should be. The discovery can also contribute to the development of new tuberculosis vaccines as well as new vaccines in general.

Tuberculosis is an infectious disease caused by bacteria. The disease can occur (and cause damage) in all organs, but it is often in the lungs. Common symptoms include persistent coughing (sometimes with coughing up blood), weight loss and night sweats. A month-long course of medication is available against tuberculosis, but if a person does not receive proper treatment, the disease can be fatal. According to the WHO, more than 1.3 million people in the world died of tuberculosis by 2022.

Against tuberculosis has also been around for more than a century the BCG vaccine, which reduces the chances of tuberculosis making someone seriously ill. The vaccine contains weakened tuberculosis bacteria. These are harmless, but should cause the immune system to act. It was already known that the vaccine protects mostly young children, but not so much adults, who tend to transmit the disease.

Quarter of research participants able to clear bacteria without vaccine

During the study, research participants, all of whom had never had tuberculosis before, were given the BCG vaccine. Through blood tests, researchers looked in the laboratory to see if cells of the immune system were able to inhibit bacterial growth. This is how Krista van Meijgaarden (PhD candidate in the department of infectious diseases) and Simone Joosten (associate professor in infectious diseases) found out that the vaccine did not lead to the immune system response needed to effectively clear the infection in everyone.

About a quarter of people were able to kill the bacteria prior to vaccination. In another quarter of the participants, it happened post vaccination. Therefore, about half were unable to clear the bacteria regardless of BCG vaccination. Furthermore, the two groups that could clear bacteria appeared to do so in different ways. That, too, was a new finding.

Response to vaccination may soon be predictable in advance

Why the reaction to the vaccine may differ, researchers do not know. Finding out is the holy grail. However, they do have strong indications that it has something to do with metabolism and the status of people's immune systems at the time of vaccination. It may be possible to predict the response to vaccination in advance by examining properties of the immune system. "For example, it has something to do about vitamin C," says Joosten. "Then you might be able to increase vaccine effectiveness by getting people to take vitamin C. Worldwide, we can make huge changes with that," she says.

Important for testing new vaccines

The LUMC researchers are therefore speaking of a breakthrough. "Before this, we didn't even know thát there were differences in the immune response. We now have solved a piece of that puzzle," explains Van Meijgaarden. The new outcomes may lead to better and more effective use of the BCG vaccine. The findings also contribute to the development of new tuberculosis vaccines. In addition, the study published in Nature Communications could also inspire other vaccine studies.