New tests are coming, in pharmacies but also do-it-yourself, to measure the level of antibodies after getting sick with Covid, or after having the vaccine while waiting for a new dose or again, as unfortunately happens more and more often due to the rate at which the Omicron variant is transmitted, if you are infected with the SarsCoV2 virus immediately before the vaccine, while waiting for the second or third dose.
In this regard, the rules established by the Ministry of Health indicate that in the event of illness the first dose of vaccine must be done within a year with a booster dose at least after 120 days, if instead you are vaccinated after one year from the disease, a second dose is also required. dose at 21-28 days, followed by the booster after at least 120; if, on the other hand, you contract the infection after the first dose, if 14 days have not yet passed, a booster dose is expected after at least 120 days, after 14 days the second dose must be taken within six months and the third after at least 120 days; if the infection occurs after the second dose, the third should be done after at least 120 days.
"In the future it could become increasingly important to identify the exact moment in which it is time to make the recall and it could also become a way to limit vaccines", observes virologist Francesco Broccolo, of the University of Milan Bicocca and scientific director of the Cerba Group. Italy.
In addition to the serological tests that can be done in hospitals and specialized laboratories, new tests have just arrived, easier and cheaper.
Classic tests for the measurement of neutralizing antibodies are reliable and, although the level may vary from individual to individual, there is a threshold beyond which one is protected and which is indicated in 500 BAU per milliliter, according to the Binding Antibody unit of measurement. Unity set as a standard by the World Health Organization (WHO). Tests of this type are carried out in the analysis laboratories, the same ones that are used for molecular tests, require the usual blood sampling and cost an average of 35 euros.
There are also other semi-quantitative tests, also based on an analysis of blood taken with the lancing device, which look for neutralizing antibodies and give a response through a colored band, whose intensity is proportional to the level of antibody titer, from 300 BAU. which corresponds to a low level of protection, up to 1,000 BAU. The cost is about half that of the tests that are done in the laboratory.
There is also a third type of test for cellular immunity which involves the determination of interferon following the stimulation of immune cells called memory T lymphocytes: the blood obtained with blood sampling is introduced into a test tube in which it is already present. a pull of SarsCoV2 virus antigens that will immediately stimulate the memory T lymphocytes. "This test was approved in early December 2021, but it is not yet well standardized, in the sense that its protective immunological correlate has not been established," notes Broccolo.
According to the expert, they are tests that in the future may be "useful for identifying the right moment to do the booster dose, thinking for example of the possibility of a fourth dose: they would help to optimize the defenses and to limit the doses".
