Polio vaccine candidate hoped to end mutation risk Speed read NOPV2 undergoing field tests in central Africa But COVID-19 blow to immunisation programmes may mar global roll-out Share this article: Republish We encourage you to republish this article online and in print, it’s free under our creative commons attribution license, but please follow some simple guidelines: You have to credit our authors. You have to credit SciDev.Net — where possible include our logo with a link back to the original article. You can simply run the first few lines of the article and then add: “Read the full article on SciDev.Net” containing a link back to the original article.