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BCG vaccine for tuberculosis protects diabetics from COVID-19: Study

The study, published in the journal Cell Reports Medicine on Monday, was conducted on 144 patients with type 1 diabetes at the start of the pandemic, much before COVID-specific vaccines were available.

August 16, 2022 / 12:49 PM IST

A widely used tuberculosis vaccine protected people with Type 1 diabetes from COVID-19, according to a study that demonstrates the potential of multiple doses of the Bacillus Calmette-Guerin (BCG) preventive against SARS-CoV-2 and other viruses.

The study, published in the journal Cell Reports Medicine on Monday, was conducted on 144 patients with type 1 diabetes at the start of the pandemic, much before COVID-specific vaccines were available.

Researchers at Massachusetts General Hospital (MGH) in the US found that 12.5 per cent of placebo-treated individuals and 1 per cent of BCG-treated individuals had confirmed COVID-19, yielding a vaccine effectiveness of 92 per cent.

The BCG-vaccinated group also displayed protective effects against other infectious diseases, including fewer symptoms, lesser severity and fewer infectious disease events per patient.

No BCG-related systemic adverse events occurred, according to the researchers. BCG's broad-based infection protection suggests that, in addition to COVID-19, the vaccine may potentially provide protection against new SARS-CoV-2 variants and other pathogens, they said.


COVID-19 Vaccine

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How does a vaccine work?

A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine.

How many types of vaccines are there?

There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine.

What does it take to develop a vaccine of this kind?

Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time.

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The researchers are hoping the results will pave the way for a large scale study of the effects of the BCG vaccine in patients with type 1 diabetes, considered among the most vulnerable groups to COVID-19.

The BCG vaccine is an avirulent tuberculosis strain Mycobacterium bovis historically given to protect against tuberculosis and, since its introduction in 1921, has been the most widely administered vaccine in the history of medicine.

Considered to be extremely safe, BCG is on the World Health Organization's List of Essential Medicines and is given to roughly 100 million children per year globally, the researchers said.

BCG is also one of the most affordable medicines, costing less than a dollar a dose in many parts of the world, they said. "Multiple studies have shown that adults with type 1 diabetes who are diagnosed with COVID-19 are at increased risk of severe illness," said Denise Faustman, director of the Immunobiology Laboratory at MGH.

"We found that three doses of BCG administered prior to the start of the pandemic prevented infection and limited severe symptoms from COVID-19 and other infectious diseases," Faustman said.

The researchers noted that unlike the antigen-specific vaccines currently in use to prevent COVID-19, BCG's mechanism of action is not limited to a specific virus or infection.

The participants in the COVID trial had previously enrolled in a clinical trial testing the effectiveness of the BCG vaccine for type 1 diabetes. Participants in the test group had received multiple vaccinations prior to the onset of the pandemic in early 2020.

"This data set is unique and exciting because the patients were all vaccinated with multiple doses of BCG prior to the onset of the epidemic," said Hazel Dockrell, from London School of Hygiene & Tropical Medicine, who was not involved in the study.

"Prior to the trial they had no known exposure to tuberculosis or prior BCG vaccination. This eliminates the major confounding factors that have limited other trials," Dockrell said.

The results support the idea that BCG needs time to have a clinical effect, but its effects may then be very lasting and durable, the researchers said.

The 144 adult type diabetics (96 BCG treated and 48 placebo) analysed in the COVID-19 trial were part of an ongoing Phase IIb clinical trial testing BCG as a treatment for adults with established type 1 diabetes.

Patients were followed for COVID-19 related outcomes for 15 months, the researchers said. Outcomes for the COVID-19 trial included: COVID-19 infection rate, COVID-19 related symptoms, reduction overall infections disease and SARS-CoV-2 antibody-level presence and intensity, they added.
first published: Aug 16, 2022 12:52 pm
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