To test, or not to test, that is the question
We have read the "sixty seconds" guidance with interest. As regards to testing for antibody levels against Covid-19, there is currently debatable information in relation to its usefulness as serological tests can vary in their individual performance characteristics (1).
Studies have explored the levels of spike glycoprotein IgG (IgG S-receptor). They have found that these may be correlated to immune response as a surrogate measure of antibody neutralization. Levels at or above 4,160 AU / ml (which correlates with a 95% probability of high neutralizing antibody titer) were observed in one study (2).
Furthermore, there has not been, to-date any solid guidance by the relevant international organizations i.e. CDC, FDA and WHO etc. The interim CDC guideline updated in March 2021 and the FDA Safety Communication issued on the 19th May 2021 both do not recommend antibody testing to assess for adequate immunity following covid-19 vaccination.
Although it is tempting to consider individuals as immune against Covid-19 when their antibody levels are exceedingly high, however until now there is no solid evidence that supports it. Therefore, in our view it would be prudent to give the booster without testing and even when the levels are known to be very high.
The answer to our title question is: not to test but boost … than "suffer the slings and arrows of outrageous fortune”.
1. Annapaola Callegaro et.al. Antibody response to SARS Cov-2 vaccination is extremely vivacious in subjects with previous SARS-2 Infection. Journal of Medical Virology 2021, July.
2. SARS Cov2 IgG2 Quantitative Assay User Manual (Abbott Laboratories Diagnostic Division 2020).
Competing interests: No competing interests