BCG Vaccine Fails to Protect Against COVID-19, Study Finds

Research debunks the idea that the BCG vaccine offers protection against COVID-19, highlighting the need for targeted preventive measures.

Highlights:

BCG vaccine was initially explored as a potential shield against COVID-19, but recent studies debunk this claim
Clinical trials confirm that BCG does not reduce infection rates or severity of COVID-19 cases
Researchers emphasize the need for targeted vaccines and public health strategies for effective pandemic control

The Bacillus Calmette-Guérin (BCG) vaccine, developed over a century ago to combat tuberculosis, has been explored for its potential protective effects against various infections beyond its primary target. This interest stems from observations suggesting that BCG vaccination might enhance the immune system's response to unrelated pathogens, a phenomenon known as "trained immunity." However, recent studies have cast doubt on its efficacy in protecting against COVID-19 ().

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‘Did You Know?
The 100-year-old BCG vaccine, once thought to offer COVID-19 protection, has been found ineffective in recent studies. #COVID19 #BCGVaccine #medindia’

Premise Behind BCG and COVID-19 Protection

Early in the COVID-19 pandemic, epidemiological data hinted at lower infection rates and reduced mortality in countries with widespread BCG vaccination programs. This correlation led scientists to hypothesize that the BCG vaccine could offer nonspecific immunity against SARS-CoV-2, the virus responsible for COVID-19. The underlying theory was that BCG-induced trained immunity might bolster the body's defense mechanisms against various pathogens, including viruses.

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BCG Vaccine and COVID-19: What Recent Studies Reveal

A comprehensive study published in eClinicalMedicine investigated the potential protective effects of BCG revaccination against COVID-19 among healthcare workers. This double-blind, randomized, controlled phase 3 trial involved participants who received either the BCG vaccine or a placebo and were subsequently monitored for COVID-19 infection rates and severity. The findings revealed no significant difference in COVID-19 incidence between the BCG-vaccinated group and the placebo group, suggesting that BCG revaccination did not confer protection against SARS-CoV-2 infection () .

Another study, published in Cell Reports Medicine, assessed the efficacy of multiple BCG vaccinations in individuals with type 1 diabetes, a group considered at higher risk for infections. Over a 15-month period, participants received three BCG vaccinations. The results indicated no significant reduction in COVID-19 infection rates among the vaccinated individuals compared to the control group, further challenging the notion of BCG's protective role against COVID-19.

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BCG Vaccine and Its Impact on Public Health Strategies

These findings have significant implications for public health strategies. While the BCG vaccine remains a critical tool in the fight against tuberculosis, relying on it for COVID-19 protection could lead to a false sense of security and divert attention from proven preventive measures. Health authorities, including the World Health Organization, have emphasized that there is currently no evidence to support the use of BCG vaccination for the prevention of COVID-19.

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What is Trained Immunity?

The concept of trained immunity refers to the long-term functional reprogramming of innate immune cells, leading to an enhanced response upon subsequent exposures to pathogens. BCG vaccination has been shown to induce such effects, resulting in reduced mortality from various infections in certain populations. However, the extent and duration of this nonspecific protection are variable and may not extend to all pathogens, including SARS-CoV-2.

Exploring BCG's Potential in Preventing Emerging Diseases

Despite the recent findings, research into the potential nonspecific benefits of BCG vaccination continues. Several clinical trials are underway to explore its effects on various diseases and its role in modulating the immune system. However, current evidence does not support its use as a protective measure against COVID-19. Public health policies should be guided by robust scientific data, and resources should be directed toward interventions with proven efficacy, such as COVID-19 vaccines, mask-wearing, and social distancing.

In conclusion, while the BCG vaccine has historical significance and continues to be vital in tuberculosis prevention, recent studies indicate that it does not offer protection against COVID-19. Individuals and healthcare providers should rely on evidence-based practices to prevent SARS-CoV-2 transmission and not assume cross-protection from the BCG vaccine.

Science evolves, and so must our strategies against disease.

References:

Safety and efficacy of BCG re-vaccination in relation to COVID-19 morbidity in healthcare workers: A double-blind, randomised, controlled, phase 3 trial - (https://pubmed.ncbi.nlm.nih.gov/35582122/)
Multiple BCG vaccinations for the prevention of COVID-19 and other infectious diseases in type 1 diabetes - (https://pubmed.ncbi.nlm.nih.gov/36027906/)

Source-Medindia