This means we do not know whether you have antibodies or not because the test did not work. This may have been because there was not enough blood in the tube you returned or because of a technical problem at the laboratory. Unfortunately, we are unable to send out additional blood collection kits for further testing. You should continue to follow government guidance on social distancing and self-isolation as appropriate. In addition, we encourage all study members to have the COVID-19 vaccine when offered, regardless of your antibody test result.