This 15-month study has surprising results: it uses an old vaccine that could be the weapon against the next pandemics (and showed 92% effectiveness against covid)

A vaccine from the past to the future? Experts are optimistic. But even so, they also call for caution. In any case: "If we had known this at the beginning of the covid-19 pandemic, we would have managed to obtain a great protective effect on the population during the first year of the pandemic"

It started as a study on the effects of the BCG vaccine on people with type 1 diabetes but quickly paved the way for another investigation - could a vaccine developed in the 1990s protect the population against other diseases and pandemics? The results are "promising", according to doctors contacted by CNN Portugal. Still, it is necessary to interpret the study "with caution", they warn.

The BCG (Bacillus-Calmette-Guerin) vaccine was developed in the 1990s to protect against tuberculosis. "It is one of the most widely administered vaccines worldwide, with an excellent safety profile as well as low cost", says Ana Sofia Baptista, medical correspondent for CNN Portugal.

Based on this principle, a group of researchers started a study, even before the covid-19 pandemic, to understand whether several doses of the BCG vaccine could have any effect on a population of type 1 diabetics to protect them from possible infections. The study had a sample of 144 participants, two-thirds of whom received three doses of BCG before the pandemic, while the rest received placebo doses.

In January 2020, when the first cases of covid-19 began to be known, researchers decided to test what had long been suspected - that the BCG vaccine could have some protective effect against other infectious diseases, namely respiratory ones.

Thus, during the following 15 months, the researchers followed the 144 participants to observe the immune system response of diabetic patients, vaccinated with at least three doses of the BCG vaccine, to covid-19. The 144 participants in the study were randomly assigned to two groups - one group consisting of 96 participants who received the BGC vaccine and another group of 48 participants who received placebo injections.

The results surprised everyone - at the end of the 15-month follow-up, six participants (12.5%) of the patients who received the placebo injection were diagnosed with covid-19. In contrast, only one participant (1%) of the 96 who received the BCG doses became infected. This group also had a lower frequency and severity of other infectious diseases.

"This is a very significant result. The probability of this being a fluke is very low. In principle, this study suggests that the BCG vaccine will be 92% effective in protecting covid-19", says Manuel Magalhães, pediatrician at the Centro Materno Infantil do Norte and Hospital Lusíadas Porto.

Denise Faustman, the lead author of the study, confirms, in an interview with the New York Times, that "the results are as dramatic as the mRNA vaccines from Moderna and Pfizer." "We've seen a big decrease in urinary tract infections, less flu and less colds, fewer respiratory tract infections and less sinus infections, symptoms that are very much associated with diabetes," adds the also director of the department of immunobiology at Massachusetts General Hospital.

Thus, the researcher continues, the BCG vaccine "seems to be redefining the host's immune response so that it becomes more alert" to contact with the virus.

Results should be interpreted with "caution"

Despite sharing the researchers' optimism, Ana Sofia Baptista, medical correspondent for CNN Portugal, says that the results have to be interpreted "with caution", taking into account, from the outset, the unrepresentative sample. "The study was carried out in a relatively small population with a specific risk factor - type 1 diabetes - and who received several doses of BCG vaccine, so these results cannot be generalized to other populations, nor to the general population. To better investigate these results, we need a larger-scale study with a longer follow-up time", he maintains.

In addition, he continues, other studies that had a larger sample did not have the same results. "In May 2022, a randomized clinical trial was published in the journal eClinicalMedicine in which no protective effect of BCG revaccination was demonstrated for the prevention of disease and hospitalization for covid in health professionals. The study included a total of 1000 participants", he pointed out. the doctor.

Speaking to the New York Times, Denise Faustman argues that her research demonstrates that it takes some time for the BCG vaccine to reach its maximum potential so that it can actually achieve the desired protective effect.

A vaccine from the past to the future?

Now that they have an idea of ​​the effects of BCG in relation to covid-19, researchers want to go further: to try to understand to what extent this vaccine can be used to fight a next pandemic, whether caused by the coronavirus, by a deadly strain of the virus. influenza or another unknown pathogen.

It is now research "for the future," Mihai Netea, a physician specializing in infectious diseases, immunology and public health, told the New York Times. Netea has already called for broader clinical trials of BCG and other vaccines that "train the immune system" to be carried out with this same goal.

"If we had known this at the beginning of the covid-19 pandemic, we would have been able to obtain a great protective effect on the population during the first year of the pandemic", he suggested.

The Open Source Pharma Foundation, an international not-for-profit organization that seeks to develop affordable new therapies in developing countries, has already shown interest in repurposing off-patent vaccines to combat potential pandemics in the future.

"Imagine if we could use existing vaccines to contain pandemics. That would change world history," said the foundation's president, Jaykumar Menon.

Should we continue to vaccinate children with BCG?

But this study raises another question: should we continue to vaccinate all children with BCG? This question is raised by pediatrician Manuel Magalhães, who recalls that the BCG vaccine was no longer administered to all children in 2016. Since then, it has only been recommended for "children under 6 years of age, as long as they belong to the risk groups", that is, "children from countries with a high incidence of tuberculosis and those who live with people from these countries are eligible".

The decision is related to the fact that Portugal has managed to reduce the incidence of tuberculosis. In 2016, less than 20 cases per 100,000 inhabitants had been registered; in 2020, 13 cases were registered per 100 thousand inhabitants.

The pediatrician does not question the National Vaccination Program, even considering it "a good program", including for tuberculosis. Now, if the effectiveness of BCG in protecting against other infections is really proven, Manuel Magalhães considers that it is a question that can be raised.

"[Para já] we cannot say now that 'maybe we should continue to vaccinate all children'. But here is an open door to this possibility", he suggests.