So exactly who is eligible for third vaccine dose now? Regular senior citizens OR Senior citizens with co-morbidities?

Senior citizens with co-morbidities. You need to provide a certificate for the same (this might no longer be true), and the gap should be 9 months.

Any idea on when regular senior citizens will be eligible?

No communication on that yet.

Regular senior citizens too, I think. CoWIN showed slots for my grandmother.

@magnificent-solstice-42554 9 months after second dose. so for 60+ and health workers who took their second vaccination on or before 9th April. My parents took second dose on 15 April 2021. They already have got message that they are eligible for booster(precaution) done on 13-Jan-2022

Thanks all. My parents also got an SMS saying they're eligible now (even though they have no comorbidities). Weird.

@magnificent-solstice-42554 According to me - all 60+ who have been vaccinated 9 months before are getting the SMS. Your parents are below 60 ?

Nope, way above 60 😂