There is no exception to veganism for a vaccine
The defining principle of veganism is that we do not exploit animals to our own benefit. Therefore, a Covid vaccine that uses animal death in its manufacture is decidedly not vegan.
Religious groups love to use medicine and life saving measures as ways to circumvent their tenets. Such is the nature of religion. The rules only apply when they are convenient.
But veganism is neither a religion nor convenient.
The basic foundation of veganism is that human life is not more important than animal life. We have no right to use animals to sustain or save ourselves.
A vaccine that uses animal tissue can never be vegan under any circumstances.