A preliminary study is claiming a relationship between countries that require citizens to get the BCG vaccine and fewer confirmed cases, as well as deaths, from the novel coronavirus disease (COVID-19).
The BCG (Bacillus Calmette–Gurin) is given in Jamaica and other Caribbean countries as a guard against tuberculosis and other other respiratory infections.
But experts from The University of the West Indies (UWI) COVID-19 Task Force have cautioned that the preliminary study does not establish causation, therefore we should be mindful to not rely too much on the findings to make decisions.
When the Jamaica Observer contacted Professor Clive Landis, who chairs The UWI COVID-19 Task Force, he said with respect to the study, members of the task force do not attach a great deal of scientific evidence to it and thus do not give it credence.
“It’s a very loose association study that was done, which has to do with vaccination coverage. There could be all kinds of reasons why outcomes might be better in [some] places because that could be used as a proxy for how strong your public health system is, what your burden of disease is. It could be hundreds of reasons. It’s certainly not a causal link that’s being established and I think, even if one was to add any credibility to the study, which really scientifically we give it low weight, the Caribbean has good coverage of BCG — and so I don’t think it is something to be concerned about,” Professor Landis said.
Furthermore, he pointed out that in fighting the viral pandemic, healthcare professionals are also tasked with fighting a misinformation pandemic, which can do equal damage.
“If the measures you’re trying to take to prevent transmission have to do with public information, then the misinformation is really damaging,” Professor Landis shared.
Meanwhile, Dr Joshua Anzinger, member of the UWI COVID-19 Task Force and director of Global Virus Network, said a big limitation of the study is that it looks at correlation and does not establish causation.
“While it looks interesting and there is pre-existing data to provide some sort of credence to this idea, there have been studies looking at the BCG vaccination prior to COVID-19 before it was even around, and looking at respiratory infections. It does appear, again, these are epidemiological studies looking to see if it has an effect on respiratory conditions, and it did. In several internationally recognised peer review journals it appears to have an effect. In several separate studies, one in Africa, one in Spain, it did have an effect in terms of decreasing disease. Not all of them showed mortality — these are respiratory infections,” Dr Anzinger said. “This has been documented before and it has been looked at as it relates to the effect of the BCG vaccination.”
As it relates to the immune system, Dr Anzinger said the BCG vaccine makes it almost on guard for a next infection.
“This has been shown by looking at people’s blood cells in a laboratory because there are effects of the BCG vaccine on the immune system. All of these things are things that are looking very hopeful, but as it relates to the BCG vaccination for COVID-19, I think there are a number of what they call confounders in epidemiology that may explain it,” he said.
Dr Anzinger further explained the possible confounders that could rule out or rule in favour of the BCG vaccine having an effect on COVID-19 morbidity and mortality rates.
“Many of these countries with BCG vaccination, Jamaica included, they tend to be in countries that are less resourced, so there tends to be less testing capacity. So it’s possible you may have people that are dying from respiratory infections but they never got a test, and so that could really be a confounding issue. Those without the BCG vaccinations that they are looking at, like the US and Europe, are much higher-resourced countries and are going to have much more as it relates to testing,” he said.
Other possibilities that could explain the correlation, according to Dr Anzinger, include the different age population distribution in countries.
“Many of the BCG-vaccinated countries have a different age population distribution. So if you compare Italy for example, which has been hit very, very badly by COVID, the population is much older than say sub-Saharan Africa, which is much, much younger on a population level, and because of that we know COVID disproportionately causes severe disease in the elderly, so that could be another factor,” Dr Anzinger stated.
The Global Virus Network director said another confounding issue could be the possibility that COVID-19 started in China, and with its spread globally, countries with the BCG vaccine started locking down earlier.
Dr Anzinger said there could also be another factor regarding COVID-19 and how it interacts with the climate.
“A lot of these countries with BCG vaccinations are in tropical regions or near the equator, and COVID-19 possibly could behave differently there. The majority of cases of COVID are, so far, in the northern hemisphere. Certainly there are cases everywhere in the world, there’s no doubt about it, that it can transmit in many different climates,” he said.
Dr Anzinger added: “As it relates to how good it can transmit in different climates, I don’t think it’s really fully known. But you can look on the map and clearly see that it is predominantly in the northern hemisphere, much more so than in the equator and southern hemisphere.”
Further, he said several countries are starting clinical trials of the BCG vaccine to see if does have an effect on decreasing disease and mortality for COVID-19, which he terms cautious optimism.
“We don’t really know for sure, because of the nature of the study. It could be reasonable that this is having an effect on COVID but we just don’t really know. Future studies looking at clinical trials of BCG and the effects on COVID-19 in these countries, I think, will be much, much more telling on whether it does in fact have an effect or not. The preliminary study is a correlation study and there could be other factors at play,” Dr Anzinger said.
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