Intensive research is being carried out worldwide to find a vaccine that will specifically protect against the sars-cov-2 coronavirus. Until there is, existing live vaccines could possibly provide some protection against infection, researchers believe.
Because live vaccines containing functional but attenuated pathogens trigger a particularly robust response from the immune system.
"Previous studies could provide evidence that these vaccines have an effect beyond their pathogen-specific effect and can increase protection against other diseases," write experts melanie brinkmann, eva kaufmann and thomas mertens in a joint response to a query from the german press agency. Such stimulation causes long-lasting changes in immune cells or their precursor cells, which lead to an increased functional readiness of the body’s defenses, emphasizes immunologist eva kaufmann of mcgill university in montreal.
"In general, there is evidence from epidemiological studies that live vaccines were able to provide "cross-protection" against unrelated pathogens, albeit at a low percentage," confirmed the president of the paul ehrlich institute (PEI), klaus cichutek. But these studies are not yet proof of such protection, he stresses. Recommendations for the use of an already approved live vaccine against the coronavirus "in any case, appropriate and convincing data, in particular on the efficacy against covid-19, were first required". To the PEI’s knowledge, such data are not currently available anywhere in the world.
Melanie brinkmann of the braunschweig helmholtz center for infection research (HZI) points to evidence that the tuberculosis vaccine BCG can protect against viral infections in humans. Whether this immune response also provides some protection against SARS-cov-2 infection is not yet known. "It is important to investigate this in clinical trials now," the virologist stresses. According to PEI, two clinical studies are currently evaluating such an effect of the relatively new BCG vaccine VPM 1002, which has already been investigated for its safety, in certain risk groups. Results expected next year.
In the journal "science", an international team of researchers also discusses the question of whether live vaccines could provide protection against covid-19. These researchers, led by konstantin chumakov of the u.S. Food and drug administration (fda), are advocating a study to investigate in particular the efficacy of the oral polio vaccine OPV – known from oral vaccination – against the coronavirus.
The vaccine, which was developed in the 1950s, has also shown some protection against other viruses, such as influenza, in earlier studies, the researchers write. "If the results of the studies with OPV are positive, OPV could be used to protect the most vulnerable populations"."
However, virologist thomas mertens of the ulm university hospital, chairman of the standing vaccination commission (STIKO) at the robert koch institute (RKI), is skeptical of this proposal: a worldwide use of the OPV vaccine against sars-cov-2 is "hardly conceivable" – especially to avoid possible infections with pathogens derived from such vaccine viruses.
The current strategy of the world health organization (WHO) is to stop all OPV vaccinations worldwide and instead to use lethal vaccination to eradicate poliovirus type 1, the only remaining wild poliovirus. "A new release of polio vaccine viruses, which is unavoidable due to vaccination with OPV, seems highly questionable," mertens emphasizes.
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