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The Antibody Test That Quantifies COVID-19 Vaccine Protection

The Antibody Test That Quantifies COVID-19 Vaccine Protection content piece image
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Some of the information in this article is based on research findings that are yet to be peer-reviewed. Results are therefore regarded as preliminary and should be interpreted as such. Find out about the role of the peer review process in research here. For further information, please contact the cited source.

As vaccines continue to be rolled out across the country, it is important for the public to understand that herd immunity cannot be validated by inoculation rates alone. Health officials and providers must now consider how strong neutralizing antibody levels (titers) will be for vaccinated individuals over time.

While two of the authorized vaccines are more than 90% effective, immunity to the virus after vaccination will inevitably wane, raising important questions: 

       How long will vaccines provide protective immunity? 

       Are vaccines working as expected in each person?

       Which vaccines appear to be creating the strongest titers, and which have the weakest (the higher the titer, the better the body’s ability to protect against infection)?

       What titer ensures safety from exposure to COVID-19?

       When should a booster be administered?

To help address these critical questions, hospitals, clinics, and private practices now have access to new neutralization assays for individuals which can improve informed decisions about vaccine deployment and better ensure the safety of the population at large.

The key determinant of protection

Neutralizing antibodies are the key determinants of protection from future infection and, for the first time, well-validated high-throughput virus-based assays for COVID-19 can accurately quantify the titers of neutralizing antibodies in individuals. The neutralization assay is a simple blood test, so it is relatively quick and easy to administer, but it provides highly specific information that can help determine future safety protocols and provide clarity about next steps for healthcare providers and vaccinated individuals.  Such monitoring can be used to better understand what levels of neutralizing antibodies are required for protection and help establish booster dosing schedules needed to sustain vaccine-induced immunity.

With the ability to regularly measure
neutralizing antibody titers in vaccinated individuals, we can understand how risk levels can change over time. For example, a titer of 500 (where the antibody is still detectable even when the blood is diluted 500-fold) provides sufficient antibody protection, but a titer of 100 may not provide sufficient protection if you are planning to get on an airplane. For the greater society, detailed, up-to-the-minute data on immunity levels can guide the next phase of recovery – evidence-based analyses of protection that will help public health officials and the entire healthcare community develop vaccine strategies designed to control the future trajectory of the pandemic.

Measuring the durability of immunity

To develop these new types of assays, researchers have been modeling the relationship between in vitro neutralization levels and observed protection from infection using data from seven current vaccines, as well as convalescent cohorts.

A recent study analyzing immunity levels to COVID-19 leveraged data from early antibody tests and indicates titers decline at least 50% (and up to 80%) within six months of recovery from COVID-19.  Within the first 250 days after immunization, models for the decay of neutralization titers also predict a significant loss in protection from COVID-19 infection. In fact, the decay of neutralization titers in vaccinated subjects over the first three-to-four months post-vaccination is at least as rapid as the decline observed in convalescent subjects. This intel also enables researchers to see how waning immunity and antigenic variation might affect vaccine efficacy.

Overall, the study proves that neutralizing antibody titers drop rapidly after natural infection. Individuals develop a wide range of neutralizing antibody titers, despite the severity of their illness. Given significant variables surrounding each individual, periodic quantitative testing can help lead to a better understanding of the decline in neutralizing antibody titers in both recovered patients and those who have been inoculated.

By monitoring neutralizing antibody levels over time, we can also be more confident in determining optimal vaccine dosing strategies, improving vaccines and immunotherapies, and reopening economies and social interactions. 

Validating test accuracy

To validate the accuracy of these new assays, comparisons have been made to the plaque reduction neutralization test (PRNT), which measures virus-specific neutralizing antibody titers and remains the gold standard for serological testing and the determination of immune protection. Based on this comparison, the neutralization assay’s titers correlate strongly with titers resulted from PRNT. However, unlike the PRNT, neutralization assays offer a widely scalable surveillance of COVID-19 protection and vaccine efficacy to meet the enormous global demand.

A recent
in-depth report published by medRxiv demonstrates the feasibility and utility of IMMUNO-COV™ v2.0, a neutralization assay for measuring SARS-CoV-2 neutralizing antibodies in vaccinated individuals and individuals recovering from natural infections. With high-quality monitoring, we can better understand what levels of antibodies are required for protection and what booster dosing schedules are needed to sustain vaccine-induced immunity. 

It is needless to say that our world felt turned upside down when the pandemic struck. However, with the rollout of vaccines
, we are finding a way out of this tragedy and back on top. With neutralization tests, we can provide targeted data and insights about how to proceed and plan confidently in the days and months ahead as the first round of vaccinations are completed. 

In short, we will have the information we need to make informed decisions about ensuring the safety of our nation, and the world.

About the author:

Dr Stephen Russell serves as Chief Executive Officer of
Imanis Life Sciences, a provider of biotechnology and pharmaceutical products and services in the fields of oncolytic virotherapy and noninvasive reporter gene imaging. A world-renowned researcher in the field of gene and virus therapy, Russell combines more than three decades of leadership as a clinician and researcher with extensive experience in all aspects of drug discovery and development.  A board-certified hematologist, Dr Russell is a co-founder of Vyriad, the Richard O. Jacobson Professor of Molecular Medicine at Mayo Clinic and President of the American Society of Gene and Cell Therapy.