LONDON, July 1 (Reuters Breakingviews) - Vaccine passports are a patchy travel fix. The European Union’s travel permits went live on Thursday, but varying standards within the bloc and the risk of the rapidly spreading Delta variant are a recipe for confusion and backsliding. Governments around the world will suffer worse headaches as they attempt to open their borders. Europe has three criteria for obtaining a vaccine certificate – a previous Covid-19 infection, vaccination or a recent negative test. The information, verified by health authorities, is uploaded to an app by passengers before they hit the airport. Israel is already operating a similar scheme costing up to $60 per certificate. New York state has gone a step further, partnering with IBM to create a pass that allows access to indoor events. Yet diverging standards undermine the feasibility of such schemes. The EU, for example, lets each country set its own rules. Thus there are 10 different sets of requirements, making it difficult for travellers to know basic things like how far in advance they should get tested. New, more infectious variants are also causing problems. Last week, Germany announced a two-week quarantine for all travellers from Portugal irrespective of vaccination status. Chancellor Angela Merkel has called for similar restrictions on Brits. At the global level, such rifts are amplified. Countries may disagree on brands of vaccine deemed acceptable. China, Chile and Indonesia, for example, are using the Chinese-made Sinovac jab, which the World Health Organization reckons has only 51% efficacy against symptomatic disease. In a possible sign of things to come, in the United States last week people vaccinated with the AstraZeneca shot were barred from a Bruce Springsteen concert. Citizens of poorer countries with minimal access to inoculation or reliable testing could face years of exclusion. Given the politicisation of vaccines and the economic stakes, the WHO has little chance of building global consensus, let alone enforcing the sort of compliance associated with long-standing diseases like yellow fever. Governments will continue to act unilaterally to protect their citizens and economies as they see fit. Some will rescind permits at a moment’s notice. Much like their holders, vaccine passports might not fly. Follow @aimeedonnellan on Twitter CONTEXT NEWS - The European Union introduced Covid-19 certificates on July 1 that will indicate whether an individual is vaccinated, has immunity because of a previous infection, or has a recent negative test result. - The European Commission said holders of the digital certificates should “in principle” be exempt from health-related travel restrictions. It acknowledged that member states could still impose curbs where “necessary and proportionate”. - The British government is also aiming to introduce quarantine-free travel for double-vaccinated holidaymakers by July 26, the first full week of the school holidays, The Times reported on July 1. - The EU has inoculated 50.2% of its population with at least one Covid-19 vaccine.