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What is BCG?
Bacillus Calmette-Guerin (BCG) is a vaccine that is used to prevent tuberculosis. Tuberculosis is an infectious disease that is caused by a hardy bacterium. The disease can affect virtually any organ in the human body but mostly affects the lungs leading to pulmonary tuberculosis.
BCG is formed from the weakened strain of a bacterium of the same species as the one that causes tuberculosis. It was developed and first used in the early 1900s. The vaccine is given as an injection to newborns. It is on the World Health Organization’s list of essential medicine.
Over the last century, the vaccine has come under significant scrutiny over its efficacy. Efficacy against tuberculosis is controversial as different genetic strains of BCG are available. This makes it difficult for scientists to reach a consensus. Even so, most analyses have shown that it reduces infection rates by 19-27%. It also reduces the progression to active infection in 71% of infected patients. It may protect patients against tuberculosis for approximately 20 years.
The vaccine has other proven uses. It has been shown to protect against leprosy. Leprosy is an infectious disease that is closely related to tuberculosis. Also, BCG has been used successfully to treat bladder cancer. BCG stimulates immune cells and is injected directly into the tumor to destroy it and prevent recurrence.
BCG and COVID-19
An ecological study undertaken early this year showed that countries where BCG was used routinely had less cases of COVID-19. The study was dismissed by the World Health Organization. Reasons included low testing rates in countries that reported lower rates and that each country was at a different stage of the pandemic.
Even so, there are two clinical trials underway on the effect of BCG on COVID-19. The aim is to find out whether BCG can prevent and/or cure COVID-19. One trial is focusing on health workers who are on the frontline, treating patients with the highly contagious disease. They will be injected with the vaccine and the rate of transmission in this highly vulnerable group will then be determined.
The hope is that like in bladder cancer, the vaccine will mount such a massive immune response, that the virus will be overwhelmed. For now, until the trials are concluded, the jury is still out. Thus, BCG has not been proven to cure or prevent COVID-19, at least not yet.
BCG and Pregnancy
As we wait for conclusive information on the effects of BCG on COVID-19, we can review its effects on pregnancy as this information is currently known and available. According to the United States Food and Drug Administration (FDA), no human studies have been conducted with BCG, but animal studies done showed significant risks to the mother and unborn baby. Thus, the use of BCG in pregnancy is not recommended by the Center of Disease Control unless the benefits outweigh the risks. In this case, the drug should be used with caution.
BCG is also not recommended for lactating mothers. This is because it’s effects on this population are unknown. It is also not known whether the drug is excreted in breast milk.
BCG has been shown to boost immunity by increasing circulating disease fighting immune cells. It is currently approved for use as a vaccine against tuberculosis and leprosy and as immunotherapy against bladder cancer. Scientists reckon that BCG as a drug is still an untapped resource. It has the potential to work against many diseases.
Perhaps it is this thinking that has led some to believe it protects against COVID-19. The judgment is sound here but nothing can be declared conclusively without proper clinical trials. Two clinical trials are already underway which is a good sign. We are likely to learn more from the scientific community in time.
Whatever the outcome of these studies, BCG is not recommended for pregnant and lactating mothers unless the risks outweigh the benefits. Thus, pregnant women may not be given this drug unless the situation is dire. Even so, any drug that will be proven useful against COVID-19 will be helpful to all, even those who cannot be given the drug. This is because it will lower the infection and transmission rates. Thus, flattening the curve.
As we wait for adequate conclusions of the two clinical trials, the World Health Organization recommends social distancing and regular hand washing as the surest prevention measures.