With over 11.5 million cases of SARS-CoV-2 (COVID-19) confirmed worldwide, resulting in 540,000 reported deaths1, researchers are looking to all available tools in the medical toolbox to prevent infections, mitigate the severity of illness and increase the chance of survival for those infected with the novel coronavirus.
A recent viewpoint published in Science2,3 by virologists affiliated with the Global Virus Network (GVN) proposes initiating randomized control trials to evaluate if prophylactic use of Oral Poliomyelitis Vaccine (OPV) could offer temporary protection against COVID-19. The authors note the vaccine provides some protection against other viral infections because it activates an innate immune response.
Coronavirus and poliovirus are positive-strand RNA viruses4, hence the virologists suggest it is likely that they may induce and be affected by common innate immunity mechanisms. OPV is a weakened version of the live virus which has been demonstrated to trigger a general immune response to any foreign organism. The researchers therefore theorize the temporary immune boost could bestow protection against viruses the vaccine wasn’t initially designed to defend against.
The authors cite large scale clinical studies of OPV for nonspecific prevention of disease performed in the 1960s and 1970s involving more than 60,000 participants which showed OPV was effective against influenza virus infection, reducing morbidity on average 3.8-fold3. According to Dr. Konstantin Chumakov, Associate Director for Research for the U.S. Food and Drug Administration’s (FDA) Office of Vaccines Research and Review, per the GVN posting, “Recent reports indicate that COVID-19 may result in suppressed innate immune responses, and thus, their stimulation by OPV immunization might increase resistance to SARS-CoV-2 as well as a broad spectrum of other pathogens.”
As the GVN researchers work with the FDA to develop a clinical trial approach to test OPV in the context of COVID-19, others are more skeptical, including public health officials concerned about the reintroduction of live polio virus to the U.S. population and in particular the risk to immune-deficient populations. Polio has been eradicated in the U.S. since 1979 and the OPV form of the vaccine has been largely phased out in favor of an inactivated formulation (IPV) which was first distributed in 1955 and has been used in the U.S. since 1987, according to the Centers for Disease Control and Prevention.
Two existing trials5,6 in Australia and the Netherlands are underway to assess whether the vaccine used to treat tuberculosis (TB), BCG (short for Bacillus Calmette-Guérin), will have a similar protective effect when administered prophylactically to healthcare workers. BCG has demonstrated its ability to induce potent protection against other infectious diseases, so called non-specific effects. The Australian study is a phase III, two-group multi-center, randomized controlled trial in up to 10,000 or so healthcare workers to determine if BCG vaccination reduces the incidence and severity of COVID-19 during the 2020 pandemic. The Netherlands study is looking to assess the protective effect of BCG as measured by reducing the number of days of unplanned absenteeism in healthcare workers.
While the polio or TB vaccines may not be the “silver bullet” that protect against COVID-19 permanently, the outcome of these trials would determine if OPV or BCG are helpful tools to buy time and reduce COVID fatalities while the global effort to develop and test a vaccine advances.