Covid: BCG vaccine does not protect health professionals – 04/26/2023 – Health

The BCG vaccine (acronym for bacillus Calmette-Guerin), normally used to protect severe cases of tuberculosis in children, did not protect health professionals against symptomatic cases of Covid, hospitalizations and deaths from the disease.

The data were published in an article this Wednesday (26) in the specialized journal Nejm (The New England Journal of Medicine) and include the participation of more than 40 researchers who work in the so-called phase 2 clinical trial group Brace.

Regarding symptomatic cases, the associated risk of having Covid in individuals who received BCG vaccination was 14.7%, against 12.3% in the placebo group (a saline substance, innocuous to the body), with a difference in risk of 2.4 points in a range of -0.7 to 5.5. This value is considered as not statistically significant.

As for severe cases, requiring hospitalization, the risk found in the group that received the BCG vaccine was 7.6%, against 6.5% in the placebo group, but this result is not significant due to the low number of cases. severe cases recorded in the study.

At the beginning of the pandemic, with the uncertainty still as to when specific immunizers against the coronavirus would be available, several research groups began testing the BCG immunizer, which generates a nonspecific immune response (that is, it is not against a pathogen, but rather produces antibodies in the body capable of fighting an infection), against different respiratory diseases, including Covid.

Initial data from studies in children in South Africa showed good protection results, as well as some laboratory tests with serum (blood) samples from patients vaccinated with BCG against Sars-CoV-2.

However, there was little evidence obtained from clinical trials, randomized, double-blind and with a control group (the so-called gold standard of studies) about its protection against the severe or symptomatic form of Covid.

With this in mind, researchers at the Murdoch Institute for Research in Children (MCRI) set out to conduct a phase 1 randomized clinical trial of healthcare professionals in Australia, led by researcher Nigel Curtis of the MRCI.

With the restrictive measures imposed by the Australian government, the number of Covid cases needed to be analyzed both in the control group and in the group that received the BCG vaccine was not sufficient to assess the protective effect of the vaccine.

Therefore, the researchers expanded the number of trial sites to 36, including four other countries, the Netherlands, Spain, the United Kingdom and Brazil, and modified the study in the second phase for an intention to treat, and not a prevention assessment (when notes the difference in risk between the two groups, not the total number of cases in each arm).

A total of 3,988 health professionals were included in the final analysis, of which 1,703 were immunized with the BCG vaccine and 1,683 received the placebo.

In Brazil, it was Fiocruz that concentrated the clinical trial centers, with researchers Julio Croda, Margareth Dalcolmo and Marcos Lacerda, responsible for conducting the analysis.

For Curtis, from the MRCI, the very fact that vaccines against Covid were developed in record time and health professionals were included as priority groups ended up reducing the number of participants and also of registered cases, which may have affected the result. Final.

“Covid symptoms reflect that the immune system is working to fight the virus. A protective response induced by BCG can be beneficial, eliminating the virus more quickly from the body, which reduces serious cases. even symptom resolution was lower in BCG-vaccinated subjects than in placebo,” he said.

Croda, from Fiocruz, says that the data presented in the research are relevant because they are the only ones obtained from a global clinical trial with a large number of participants, but that in the context of health professionals in the country it is not possible to say that BCG protects against symptomatic infection or severe cases of Covid.

An important point is that more than 64% of the health professionals included in the study were evaluated in Brazil, showing the importance of including Brazilian researchers in the analysis. The country was also one of the most heavily affected by Covid, with a high number of deaths in the general population and also cases and deaths in health professionals.

“The burden of Covid was very high in the country, and this demonstrates how populations at greater risk, such as health professionals, were at the mercy of the virus”, he says. In smaller and observational studies, however, there was some kind of protection, although this was not supported by the Brace study. “It is possible that the protective effect in older individuals, with nonspecific immunity, is smaller, while in children it is a greater protective response”, she says.

Although the observed results indicate that BCG does not have a protective activity in adults, it may have a role for other viruses and respiratory diseases.

“We are also conducting two other studies with data from the Brace trial to assess the response against the herpes simplex virus, which has a high rate of reinfection, and protection against latent tuberculosis, since health professionals who care for patients with tuberculosis have high risk of bacterial infection as well.”