Last reviewed 21 December 2021
The Department of Health and Social Care (DHSC) has issued updated information for healthcare workers on the types of Covid-19 antibody tests available and how to interpret results.
The DHSC’s document, Antibody Testing for SARS-CoV-2: Key Information, said that, as more people access antibody tests, there is an increasing chance that people approach healthcare professionals for advice.
The guidance was produced to help healthcare workers in interpreting results and in discussions with patients regarding antibody testing, vaccination, infection and risk. It should provide guidance to professionals but isn’t intended to give direct clinical care.
Testing for anti-SARS-CoV-2 antibodies used to understand vaccine effectiveness, monitor the impact of variants of concern (VOCs) and estimate prevalence of infection.
It can be used to distinguish active infections from persistent PCR-positivity, where dead parts of the virus are still detectable on a PCR even though these cannot infect anyone. It can also be used to see if a patient is likely to benefit from monoclonal antibody treatments in hospital.
The guidance says 99% of people generate antibodies after a full schedule of vaccination and this response is anticipated to remain detectable for at least 10 months. However, waning mechanics are not fully understood and vary between individuals.
It says that antibody status alone cannot be used to confidently assure against protection from infection, although the presence of detectable circulating antibodies will almost certainly result in a mitigation of disease severity on exposure to virus.
Waning of antibodies below detectable range over time will likely not result in loss of protection from severe disease but infections are highly likely to be possible.
Different variants are more likely to evade any protection afforded by previous infection by another variant or by vaccination but disease severity is still likely to be mitigated.