India is facing its largest COVID-19 crisis since the start of the pandemic, as infection numbers rise to more than 400,000 daily, a record high in the world. Researchers believe the surge is caused by a confluence of factors including high social mixing, less adherence to protective measures and low vaccine coverage. But an overriding reason for the explosion in spread is due to the emergence of the highly infectious "double mutant" Indian variant. 

What's worrying about the Indian variant is that it has two critical mutations that make the virus bind more effectively to human cells. This results in a virus that is more transmissible and which has the ability to escape the human immune system. That means it could evade antibodies created by a prior infection or by vaccination.

With the variant fast spreading to more than 17 countries, governments are once again responding with border closures and increased restrictions in order to fight back. For now, COVID-19 vaccines have been found to work on the Indian variant although experts fret that future variants could be more immune-evasive. 

On a brighter note, the world has achieved an unprecedented feat of one billion COVID vaccinations in four months. Scientists believe that hitting the two-billion mark could happen even faster, with hopes that widespread vaccination of 75% of the world population could finally bring the pandemic under control.