Well, few thing that might become important come to my mind,
1. once the country know about the cure, they can use that cure and monopolize the cure to negotiate whatever problem they may had with other countries
2. There might be some important figures that died during that 7 year who, if live, might be a important key to unforeseen event.
3. From 1., MC country might see an uprising of economic and/or might shift in power compare to other country.
You can also see how COVID-19 change our world during 2-3 year of pandemic. If the cure or vaccine has been found earlier, many people might not have to suffer like what we have or in some scenario, we might be able to prevent the COVID-19 pandemic all together.