1.   All patients in group A were symptomatic at initial presentation.

2.   One option would be the use of enhanced-potency, inactivated poliovirus vaccine, which induces detectable neutralising antibody in almost all recipients after three doses.

3.   And some people seem to have Lyme disease without any detectable antibody response.

4.   The difference results from the longer time required for the body to create detectable antibodies to hepatitis B and C than for the HIV virus.