 Well there are four phases in terms of clinical development of a vaccine. The first phase is actually when you first put a vaccine into volunteers for the first time. That's called phase one and it's usually in small numbers, tens of volunteers. And there you're looking at predominantly the safety of the vaccine. Is it safe? How well is it tolerated? What are the side effects? The second phase is then to move into a few hundred individuals and continue to look at safety and say what kind of immune response does the vaccine induce? If that goes well and it still looks safe then you move into phase three which is looking at how well the vaccine protects against an actual infection. If that's successful and you show that the vaccine works really well and still continues to be safe then you may be able to get a licence for that vaccine and start to roll it out in the wider community. But that's the fourth phase where you still need to track safety for a prolonged period of time, several years. We think that those first vaccines probably may well be more effective against disease preventing people from becoming sick than blocking transmission. Ideally we want a vaccine that's 90% effective. The first vaccines may not get there so we don't know what threshold is required to make a vaccine worthwhile moving out as a public health policy. Making a vaccine for seven billion people has never been done before. I think the logistics of getting a vaccine out to those people that need it is a significant undertaking. It's not going to happen in days, weeks, months. It's more likely to happen over a year or even several years and there may well be a requirement for booster vaccinations even on an annual basis. So this is something where it's going to be a long haul to make sure that everybody's protected against COVID-19 for the foreseeable future.