COVID-19 and non-specific actions of BCG vaccine and poliomyelitis vaccine. Professor Evans, one of your expertise areas is in assessing the non-specific effects of vaccines. You were who global Advisory Committee on vaccine safety member, you worked at the UK medicines Control Agency and dealt with major vaccine safety concerns. And it's a very hot topic today, by potential ability of BCG vaccine, vaccine against tuberculosis and poliomyelitis vaccine to stimulate innate immune system in general, and possibly to lower the infection risks for COVID-19 Coronavirus. And the basis of such hopes is data from studies on vaccinations of newborns with BCG vaccine, and also with poliomyelitis vaccine and possibly with MMR vaccine, and it showed that vaccination decreased mortality from unrelated respiratory viruses, from pneumonia and from sepsis and often by substantial percentages. But most interestingly, in one of your papers, you publish that their results in the reduction of the death rates accrued mostly in the first three weeks after the vaccination. So, you know, these results could have shown that it's a statistical kind of error rather than the really observed effects because the children could have been selected for or against vaccination. And it's actually very interesting that recent analysis from Israel shows that the influence of childhood BCG vaccination are on the risks of COVID-19 Coronavirus infection has showed no difference it listing young adults. So, that doesn't give us information whether the fresh real vaccination of adults with BCG vaccine or poliomyelitis vaccine could still help reduce risks of COVID-19 infection. What are your thoughts on the nonspecific effects of BCG vaccine on oral poliomyelitis vaccine Or parenteral per poliomyelitis vaccine and possibly an MMR vaccine to prevent other respiratory infections and possibly to reduce risk of infection with COVID-19. You know, from what I've said earlier that I'm not a virologist, so I can't give an opinion as a virologist. What I can say is that we do know that vaccines can have effects generally on the body that are more than simply against the virus or other disease that the vaccine is intended to treat. So such nonspecific effects can occur. And so one of the fascinating things is that BCG is effective in certain forms of cancer, particularly in relation to bladder cancer. So they can have effects that are surprising to us. The problem is that when we do observational studies on these, particularly when we're dealing with children in low and middle-income countries, the sort of children who get particular combinations of vaccines are not getting them at random. And it is very difficult to sort out what is a genuine effect from something that is simply a selection bias in those who get the vaccine. So, one of our problems is that if we do not do sufficiently large trials, we cannot sort out how many of these nonspecific effects are genuine and how many are not. Now when it comes to assessing the effect of BCG vaccine and a range of childhood vaccines on COVID-19. Often we have a major problem because the childhood vaccination programs in many countries are extraordinarily effective. And so very, very large numbers, a large proportion of the children do get those vaccines. And the children who don't get them are really quite different. And so trying to disentangle the differences in the children who happen to have the vaccine from those who got the vaccine, who didn't get the vaccine is very, very difficult. So I think that observational studies are quite difficult to interpret. But certainly, so far, we have no strong evidence That giving these other vaccines has an effect on COVID-19. One of the problems, as I said earlier, is that COVID-19 seems to be a very complex disease. It is not only affecting the lungs, but it seems to be affecting the lining of the blood vessels. It's leading to rather strange effects in the coagulation. We're not sure how easy it's going to be to clear the virus from the nose even with vaccines. And we know already that the most sensitive the best test for COVID-19 in terms of clinical symptoms, rather than being able to measure the virus directly is a sudden loss of taste or smell. And so the virus is obviously having a dramatic effect in the nose. Whether we can deal with that with a vaccine, we simply don't know. So a number of the vaccines that have been suggested to have benefits in pneumonia, or other simple lung diseases may even if they were effective in those diseases may not be effective in COVID-19. So we have to do trials, and I believe there are some trials of the other vaccines that are existing already in COVID-19, but we have no convincing evidence from them, yet.