I'm trying to figure out when Kelvin may have arrived on the island and whether it was before or after the purge. If it was before, that would explain why he was left there all alone and why he survived -- because he was down in the hatch. So while everyone else was being gassed aboveground, Kelvin was blissfully unaware, until one day, somehow, he found out about it. Maybe he saw the dead bodies and mistook it for a plague and started wearing the hazmat suit for protection against what he believed was a sickness. Someone off the island may even have sent him "vaccine" as protection to keep him down there rather than have him know what really happened.

So does this mean there's no sickness and it was really a chemical attack? If so, why did Kelvin believe the injections would protect him? Did someone tell him that? Based on what we saw last night it would seem that Kelvin was the lone survivor of the purge.

Well, don't forget that there was Radzinski before him, too.

It's hard to say. Seems like he came to the Island in the late 1990s, and I don't know if the purge was before or after.

Kelvin did say that he actually joined the Dharma Initiative ("namaste"). The thought of him actually being down in The Swan pushing the button during the purge is compelling. My next question then is why he was waiting for "him". What made him think that a "him" was coming?

those were his orders, to wait for replacement... which never came...

I'm pretty sure he joined just shortly before the purge.
Also I'm pretty sure I saw someone getting injected with the "vaccine" during Ben's flashback to the early days of the island. I guess they've been doing that since the begining, I wonder what they are vaccinating themselves from?

I've always assumed Kelvin came on board in the 90's - after the Gulf War..

If that's the case, I'd guess that Ben, Richard, and the others made up "the purge" to cover for the fact that they assasinated most everyone in their community. If that's the case, I'm thinking there is no sickness... The vaccines were a cover to help perpetuate the lie of the "purge".

I think Kelvin is Jacob. The "Help Me" sounded an awfully lot like his voice and when I watched frame by frame the silhouette looked like Kelvin with longer hair. Remember the blood splattered on the ceiling in the hatch? Kelvin said that was a result of Radzinski's suicide but what if it was really a result of Kelvin infiltrating the hatch, killing Radzinski during the purge and taking over the station?

When Desmond unexpectedly arrived, Kelvin (Jacob) had to act as if all was normal on the island. He thought Desmond was part of Dharma and the 'Hostiles' wanted to ensure that 1) the supply drops continued and/or 2) The outside world continued to believe that all was well on the island and there was no reason to come investigate. With Ben spending his entire youth as a "spy" for the hostiles, he had plenty of time to gather all information needed for the hostiles to carry on the ruse that normalcy was being maintained on the island.

That is exactly why Kelvin (Jacob) had to scout the island draw a map of all possible stations/hatches, etc on the blast door. A real member of Dharma would have had easy access to that information.

Could Kelvin/Jacob be a prisoner on the island? Remember when they were approaching his hut there was that mysterious line of gray powder on the ground that Locke stopped to investigate? I have a feeling that stuff was surrounding the hut, acting as some type of barrier and keeping Kelvin/Jacob (or whatever that spectre-type thing was) from leaving the enclosed area. Anyway, just a thought.

I'm pretty sure he joined just shortly before the purge.
Also I'm pretty sure I saw someone getting injected with the "vaccine" during Ben's flashback to the early days of the island. I guess they've been doing that since the begining, I wonder what they are vaccinating themselves from?
I think that relates to the quarantine signs on the bunker doors and probably to the inicident which happened a long time even before Ben came to the island.