Is post-COVID-19 vaccination antibody level check necessary?

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Bachti Alisjahbana Staff Lecturer, Tropical Diseases and Infections Division, Internal Diseases Department, Dr. Hasan Sadikin Hospital and Head of Padjadjaran University Research Center for Care and Control of Infectious Diseases (RC3ID)

IO – COVID-19 vaccination is meant to fortify the immunity of individuals and groups against infections or heavy illnesses which may offer opportunities to the disease. Vaccination will generate antibodies and immunological memory that will prevent that from happening. The benchmark of success for the currently-massive immunization program is “how many people can become vaccinated within a population”. As the target of immunization is to generate antibodies, an antibody level check performed post-vaccination would be more objective. For COVID-19, the test target is the level of antibody-to-Receptor binding domain (Rbd) or neutralized titration antibodies.

This idea is not new. Many people have already asked, “Will I have sufficient antibodies after COVID-19 vaccination?” especially since reports say that the efficacy of Sinovac vaccine is only 65.3%. However, the Ministry of Health, the WHO, and the CDC of America have not yet declared that this check is necessary.

Let’s look at some benefits of determining antibody levels, in terms of individual and group interests, and what we know of this technology.

Individual Benefit

It is entirely normal for a vaccinee to wonder whether they have sufficient anti-COVID-19 antibodies to protect them. In fact, just about everyone questions this, and thus compares their post-vaccination antibody levels independently. However, such doubts should be even more relevant for the elderly or for those with specific co-morbidities. Immunity response in the elderly of 60 years and higher is known to be lower, even only 35%. Antibody formation response in sufferers of diabetes, chronic kidney failure, chronic lung illness, and HIV-AIDS is also low.

A COVID-19 survivor would have asked, “What’s the use of vaccination for me as a survivor?” After all, most COVID-19 survivors show a high level of Coronavirus antibodies, up to 6 months after their sickness. It is highly understandable if they want to know their own antibody level before they decide to accept vaccination.

An important benefit of vaccination for individuals is for travel purposes. More and more countries demand COVID-19 vaccination another kind of passport or visa, as a requirement for entry. For this purpose, COVID-19 antibody test results are a more accurate measurement than a vaccination certificate. Certif-

icate forgery is rampant because of the expense and difficulty involved in swab-PCR testing. On the other hand, antibody certification is easier, faster, and cheaper, is a more reliable indicator of resistance to the Coronavirus, and it can be part of a standardized travel requirement.

Furthermore, this requirement is not new. CDC America suggests the need for antibody checks for the Morbili virus (the cause of measles) or a Morbili vaccination certificate prior to leaving the United States.

Benefits for the Community

Mass vaccination benefits the community by generating “herd immunity”, only achieved when 70% of the population become immune to any specific disease. As studies confirm, people who have COVID-19 antibodies are protected from the disease. If the vaccine’s efficacy is only 65.3%, we can interpret this to mean that 34.7% of the vaccinees are not effective. With this performance level, how can we be sure that when 70% of the population is vaccinated, we achieve herd immunity? A rough calculation means that with this efficacy rate, when 70% of the people are vaccinated, less than half of the population (65.3% x 70% = 45.7%) becomes properly protected. That’s a far cry from the herd immunity target.

The determination of antibody levels generated by mass vaccination programs is a more objective benchmark of achievement. This is because the failure of sufficient immune response in a community can happen because of one of these causes: 1) vaccine effectiveness is less than. 100% (as in the above sample), 2) co-morbidity is not considered, and 3) operational failures, such as vaccines getting damaged or improperly refrigerated during transportation.

If we implement a COVID-19 antibody level check before vaccination, we will have the added advantage of finding out how many people already have sufficient levels of antibodies. With such an intense pandemic, the prevalence of people with positive antibodies may reach more than 10%. If we find who these people are, we can save money and effort by restricting vaccine distribution to people who do not have sufficient antibodies. We can still achieve herd immunity with a 10% increase of efficiency in vaccination.

State of the Art COVID-19 Antibody Testing

The first weakness of the COVID-19 antibody level testing is that we don’t know for sure the effective antibody level threshold likely to prevent illness, or the “correlate of protection”. We have already found out the threshold to achieve for some diseases. For example, in vaccination for Diphtheria, the antibody level sought is ≥ 0.1 IU/mL. This level is considered sufficient to provide reliable, long-term protection.

The second weakness is that antibody level will decrease gradually over several months, to undetected levels. However, that does not mean that the protective force is gone. We do not know yet when we should check for COVID-19 antibody levels or how long vaccination protection lasts. Some vaccines will continue to

protect us, even though no post-vaccination antibody levels are detected. For example, in the case of Hepatitis B vaccination: even though antibody levels are not detected for decades after the vaccination, we will still be well-protected against Hepatitis B.

Determining the correlate of protection requires the study of thousands of people. We believe that researchers all over the world are doing this as we speak. However, is that enough information to support vaccination programs in Indonesia? Our condition is different from that of the United States, which uses vaccines with an efficacy rate of > 94%. We need to note this, as Sinovac is currently considering the need to administer a third vaccination.

If a third vaccination is indeed to be performed as immunity booster, another benefit of the post-vaccination antibody check is to filter out those who really need this booster from those who don’t. This will make the distribution of the third vaccination more efficient and on target.

Conclusion

We consider a post-vaccination antibody level check as essential, a move which must be seriously considered by Government and health experts. It is very important to ensure that we are all individually protected, and it is important for the community to ensure the efficiency and effectiveness of vaccination programs. We believe that the technicality and standardization of testing is something that Indonesian biomedical experts and health workers are more than capable of determining.