Regularly, the vaccines that are applied to prevent or reduce the effects of diseases that can be transmitted between person-person or animal-person, are usually transported and/or stored at temperatures close to or below freezing (commonly, 4ºC, – 20ºC or -80ºC). The lower the temperature necessary to maintain the stability and/or viability of a vaccine, the greater the challenges of getting it to all corners of a country; It is worth remembering the case of the Pfizer and Moderna vaccines against COVID-19, which precisely required preservation at -80ºC, while AstraZeneca’s was enough to be able to protect it at -20ºC. In any case, the need for refrigeration remains and thus the challenges for a vaccine to be in appropriate conditions until the moment of its application, that is, that it does not lose or significantly reduce its ability to stimulate a protective response.
In the line precisely of maintaining the stability of the vaccines at temperatures other than refrigeration or freezing, it is interesting to note that the results of a phase 1 clinical study conducted in the United States (that is, in a population that has not been vaccinated with BCG), with the TB vaccine candidate named ID93+GLA-SE (https://doi.org/10.1038/s41467-023-36789-2), both in a thermostable presentation (it can remain active for up to 3 months even if it is kept at 37ºC), and in a “conventional” one that does require refrigeration.
In this work it was found that both formulations, thermostable and conventional, were equally well tolerated, causing mild adverse effects and without being different between them. In addition, both had the same ability to induce cellular immune response (mediated by CD4+ T lymphocytes) ex vivo, while the thermostable formulation improved the ability to induce antibody response compared to the standard vaccine prepared and maintained today.
These results represent good progress in the field of achieving a reduction in complications in transport and storage until the application of vaccines. Obviously, various questions arise, including whether or not this ability to maintain safety and immunogenicity will result in better protection against TB in people. Of course, one wonders if the process used to prepare the heat-stable version of ID93+GLA-SE could be extrapolated to other vaccines in use today that still require refrigerated or frozen temperatures. It should also be recognized that the study population was relatively small (less than 50 people), mostly of a single racial characteristic (white) and of a single sex (female), so it would be extremely necessary and interesting to validate these results in populations of characteristics different from those reported in the cited study.
*Dr. Flores Valdez, author of this article, is a Titular C researcher at CIATEJ, AC in the area of Medical and Pharmaceutical Biotechnology. Doctor of Science with a specialty in Biochemistry from UNAM. He completed his postdoctoral fellowship in Microbiology and Immunology at the Stanford University School of Medicine. Research Member of the international network VALIDATE “Vaccine development for complex intracellular neglected pathogens”. Holder of patents as inventor before the IMPI for the candidate for a new vaccine against tuberculosis.
