The Missing Link: COVID-19 Antibody Tests Need Buy-In From FDA

Source : IN VIVO

Along the patient’s journey of care for COVID-19, the use of antibody testing can play a critical role in the decision-making and management of the virus.

These tests not only measure whether the immune system has reacted to a virus or vaccine, but can further inform medical decision-making. Yet antibody tests for the COVID-19 virus have been beset by a lack of understanding about their value in combating the pandemic.

Throughout the pandemic, health care workers have relied on testssuch as PCR and antigen tests – to tell if individuals have been infected with COVID-19, and to help inform quarantine guidance and planning. These diagnostic tests results give clinicians and the public the clear directives they seek.

Ross Molinaro

But as vaccines continue to be administered throughout the US, we must evaluate vaccine durability across populations. While antibody tests provide crucial data about an individual’s immune system response, this type of data is critical on a larger scale, too. It serves as a foundation for understanding how specific populations are responding, or not responding, to the COVID-19 virus and its vaccines.

Governing organizations, like the Centers for Disease Control and Prevention and the World Health Organization, continue to make broad recommendations for the masses, providing a roadmap for the most common scenario. This is the appropriate, responsible approach. However, there are populations that do not fit into these generalized guidelines.

Those who do not develop a lasting immune response to COVID-19 infection or immunization include cancer patients, transplant recipients, elderly patients whose immune systems wane, the immuno-compromized  ̶  and even those who have experienced mild or asymptomatic infections with transient immunity, which means the immunity lasts only a short while.

Those with continued re-exposure to the virus and its variants may also need to be monitored more closely after vaccination, particularly highly exposed workers, such as people who work in long-term care facilities, health care workers and first responders.

In addition to those at-risk groups, the US’s most vulnerable population includes older adults, especially those with underlying health conditions like diabetes, obesity and lung disease. As we get older, we experience a natural, gradual decline of the immune system, which starts to lose its memory of previous exposures.

'It is in the interests of individuals and public health officials to use antibody testing to determine how long vaccines will keep the public safe.'

We see this with many traditional vaccines where boosters are often needed  ̶  tetanus, whooping cough (pertussis) and shingles (chickenpox). Because the elderly population was among the first group to receive vaccinations, its members could potentially be the first to experience a waning immune response.

Using available, high-quality antibody testing to track immune responses over time will help us to determine whether and when they might need a booster shot. To protect against another potential outbreak, especially in the most vulnerable, we should begin this testing system now.

Richard Frank

These at-risk populations have not yet been studied extensively or systematically in vaccine clinical trials. Some critical questions remain. It is in the interests of individuals and public health officials to use antibody testing to determine how long vaccines will keep the public safe.

The use of accessible, high-quality and reliable COVID-19 antibody testing with a clear implementation protocol can help confirm vaccine efficacy and promote public health.

While COVID-19 is being studied on a global scale, some individual physicians have been using antibody testing to supplement their knowledge of how effective vaccines will be for their patients in the long run. Dr. Kevin Latinis is a rheumatologist in the Kansas City metropolitan area who serves as medical/scientific advisor for the Cass County COVID-19 Task Force. Latinis has a PhD in immunology and serves as a consultant for applications of immunologic testing.

As an immunologist, Latinis knows the importance of understanding how the body responds to natural infection and vaccination. He said: “I want to know if immunity remains potent and enduring enough to provide long-term protection against exposure to the virus.”

Additionally, antibody testing can provide a basis for tailoring recommendations to specific individuals.

For example, one of Latinis’ young lupus patients who had previously tested positive for COVID-19 developed a significant lupus flare shortly after the first dose of vaccine. He and the patient weighed the benefit of COVID-19 immunity against the risk of an autoimmune flare. When Latinis performed antibody tests on the patient, he learned that their antibody levels were already high. That reassured him that the patient’s COVID-19 protection was in place to keep their underlying autoimmune disease from worsening.

Latinis continues to order antibody tests for use in selected patients to track how they respond to vaccination. Knowing whether members of these vulnerable populations achieve an appropriate immune response to the vaccine is clinically meaningful. “As we continue to learn the persistence and durability of one’s immune response to SARS-CoV-2, knowing the quantitative antibody response will inform clinical decision-making and lead to better, individualized medical care,” Latinis said. “In line with the fundamentals of quality medical practice, we should use antibody tests for COVID-19 to inform and guide clinical management.”

To date, no SARS-CoV-2 antibody tests have been authorized by the US FDA for the use in evaluating the immune response following vaccination or to assess immunity. As reiterated at a recent FDA town hall (23 June) by Tim Stenzel, the CDRH director of the Office of In Vitro Diagnostics and Radiological Health (OHT7), the FDA is not actively reviewing tests to identify immunity to COVID-19. Further, the FDA is recommending that manufacturers do not invest in developing of assays that measure vaccine-induced immune responses unless and until federally funded studies on immunological responses to vaccination are complete.

When the FDA begins accepting SARS-CoV-2 antibody tests for the measurement of immune responses in vaccine recipients, manufacturers are ready to answer the call by validating their high-quality assays and submitting to FDA review for this purpose. 

By Ross Molinaro, Richard Frank