Hi Kit Kit,
The vaccinations which your children received obviously have not been proven to produce any protective antibodies yet. This suggest there is either no antibody production at all (i.e. non-responder) or antibodies at too low a level to be detected by routine methods after some years.
One commonly employed way to distinguish the two is to provide a booster dose given as an injection and to check for the protective antibodies 1 month later.
A person having a low antibody level with previous vaccination will usually mount a response to produce detectable antibodies this time while the non-responders will not. Once antibodies are detected to be above the threshold level with the booster injection, no further action is required.
For a non-responder, a 2nd vaccination cycle which include 2 more doses (the 2nd and 3rd 'booster' doses) will be required to hopefully induce a response. To avoid any confusion, some doctors may advise a 2nd vaccination cycle straight away skipping the booster trial. This explains the different protocols you mentioned.
- Dr Quan
