Lambert can be seen getting a vaccination for small pox between mission 4 and 5. Lambert was born in 1961, meaning he attended primary school in the mid 1960's and early 1970's. At that time school children were routinely given several vaccination, including small pox, making the vaccination unnecessary and wasteful. Nearly all Americans over about 30 in 2006 would be immune to that virus.
The goof item below may give away important plot points.
At the end of the game, when Sam manages to get his hands on the last ND133, he says to Lambert that there are 11 minutes left on the box, 5 less than Lambert had hoped for. However, in the following cinematic, we see Sam running with the ND133 in his hand with a timer that's just passed the 12 minute mark.