Kids jab and protection?

Kids currently have to have 2 jabs 3 weeks apart. Does anyone know how much protection they will have between having the first and the second jab. My kids had theirs 2 weeks ago and are due for their 2nd next week. They spent a day at the weekend with a relative who has come down with the flu. Just wondered if they should have produced any antibodies to give them some protection?

They would have some kind of protection, but to get the full effect they'd need both jabs. So there is always a chance they could come down with it, however the incubation period is what 72 hours, so just keep an eye on them.