According to Dr Ashish Kamat, a co-author of the study, the incidence of the disease and mortality rate from COVID-19 has been ten times higher in countries which did not have mandatory BCG vaccinations, which are given at birth for tuberculosis (TB), Economic Times reported. Dr Ashish is a Urologic Oncology professor and cancer researcher at MD Anderson Cancer Centre in Houston, Texas.
COVID-19 has affected over a million people worldwide, and has sent entire countries into lockdown and brought economies to a halt. The global death toll is well over 53,000.
The study, called “Correlation between universal BCG vaccination policy and reduced morbidity and mortality for COVID-19: an epidemiological study” was published on medRvix, a website that posts unpublished medical researches. It has not been peer reviewed.
What the study says
The study has looked at COVID-19 cases and death rates between March 9 and 24 in 178 countries. 21 of these did not have a BCG vaccination policy, while there wasn’t clarity on this for 26 countries. So, these 26 were treated as not having a BCG policy by the researchers. “Middle high and high-income countries that have a current universal BCG policy (55 countries) had 0.78± 0.40 deaths per million people. In contrast, middle high and high income countries that never had a universal BCG policy (5 countries) had a larger mortality rate, with 16.39 ± 7.33 deaths per million people,” the study found.
The US has quickly become the epicenter of the virus, and Italy too has been heavily impacted, with death toll crossing 6,000 and 13,900 in the two countries respectively. The study compares Italy and Japan. The former, which introduced strict social distancing norms but has never had BCG vaccination, is seeing a high number of cases and deaths. Japan by contrast, has had a BCG vaccination policy since 1947 and is seeing a lower death rate despite not enforcing strict social distancing norms.
The study hypothesizes that the lower mortality and morbidity can be partially explained by whether populations were given BCG vaccinations. It also said the BCG vaccination was more effective in protecting the elderly, who are also more vulnerable to the novel coronavirus. “For instance, Iran has a current universal BCG vaccination policy but it just started in 1984, and has an elevated mortality with 19.7 deaths per million inhabitants. In contrast, Japan started its universal BCG policy in 1947 and has around 100 times less deaths per million people, with 0.28 deaths. Brazil started universal vaccination in 1920 and also has an even lower mortality rate of 0.0573 deaths per million inhabitants.”
Attempting to address why China, despite having a BCG vaccination policy in place since the 1950s is severely affected, the researchers argue that between 1966 and 1976, during the Cultural Revolution in the country, TB prevention and treatment agencies were disbanded or weakened. “We speculate that this could have created a pool of potential hosts that would be affected by and spread COVID-19. Currently, however, the situation in China seems to be improving.”
The study also says that BCG vaccination only partly explains the lower mortality and morbidity to COVID-19 in some countries. A lot more depends on factors like the healthcare infrastructure and capacities of the countries as well as how much they are testing.
What role does the BCG vaccine supposedly play?
The BCG is a live attenuated strain that comes from an isolate of Mycobacterium bovis, which is related to the TB causing pathogen Mycobacterium tuberculosis. However, apart from just treating TB, the BCG vaccine, like some others, produces a “positive “heterologous” or non-specific immune effects leading to improved response against other non-mycobacterial pathogens,” the study says.
This essentially means that BCG can, to an extent, help protect against unrelated infections as well. It seems to train the body’s immune system to generally fight better against infections.
Apart from TB, the BCG vaccine is also used against early stage bladder cancer – it prevents the cancer from growing and prevents it from coming back. It is also used to prevent leprosy. Studies have shown that it can help reduce and protect against other respiratory infections in children.
The researchers pointed out that BCG vaccine-stimulated general immune response and the data (countries with BCG vaccination programs having lower mortality) could identify a possible correlation between vaccinated populations having lower COVID-19 incidence and mortality.
Interestingly though, BCG’s effectiveness against TB itself has varied, and has even been debated.
Meanwhile researchers in Australia are now set to conduct trials to test the BCG vaccine for its effectiveness against COVID-19. The Murdoch Children’s Research Institute, which will do the trials over a period of six months, says that this is for the protection of healthcare workers, and will enroll around 4,000 of them across Australia. A similar research is going on in Netherlands.
Word of caution
While this could be good news for countries like India, which has had a BCG vaccination policy since 1960s, experts warn that it is too soon to jump the gun.
Sam Behar, a professor at the Department of Microbiology and Physiological System, University of Massachusetts Medical School told Down To Earth that while this is an interesting hypothesis, it is just a hypothesis at this point.
Gagandeep Kang, a microbiologist and Executive Director at Translational Health Science and Technology Institute, told The Hindu that only actual data which proves that BCG vaccinated people are less disease prone can be convincing of the theory. He also said it’s wise to wait for results of trials that are taking place in Australia and Netherlands.
The study in question itself suggests that randomized controlled trials are needed to determine BCG-triggered response to COVID-19. “BCG is generally innocuous with the main side effect the development of inflammation at the site of injection. However, BCG is contraindicated in immune compromised people as well as pregnant women, so care should be taken when applying these possible interventions for COVID-19,” the researchers say.
Read: When will we have a treatment or vaccine for COVID-19? Here are some developments
Source: TheNewsMinute.com