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COVID Boost With A Third Dose.

Waning antibodies call for a booster shot. Here’s why you may need one.



On August 8, 2021, U.S. health officials from the U.S Centers for Disease Control and Prevention (CDC), National Institutes of Health (NIH), and the Food and Drugs Administration (FDA) presented evidence that the current level of protection the vaccinated have against Covid-19 infection is waning, as the highly contagious delta variant continues to spread.

It is not unusual for a vaccine to lose protective power although there are some that offer lifelong protection against a virus, such as the one created specifically for measles. However, the expectation comes along partly because medical history has evidenced that the natural immunity people develop against milder coronaviruses has often shown a decline in efficacy over a certain period of time.

While the country plans to start offering Covid-19 booster shots to all Americans beginning the third week of September, some experts say the data presented are still not strong enough to move forward with plans for booster shots. This has caused concern from the public and again, a division is mounting.

The key measure of vaccine effectiveness has been the ability to prevent severe illness and death, not simply infections, even among the most vulnerable populations. Let us weigh in on the current issue of booster shots, waning antibodies, and understand for ourselves why we need to have a COVID boost of the vaccine.

Covid-19 immunity and neutralizing antibodies.

Researchers and medical experts have earlier presented suspicion on the immunity provided by Covid-19 vaccines and how immunity will wane over time. At a conference hosted by The Wall Street Journal held in June of 2021, Dr. Anthony S. Fauci, NIAID Director (NIH) stated that “Historically, at least with the coronaviruses, the mild common cold coronaviruses, the durability of the protection from infection isn’t very long”.

According to data published by Pfizer, antibody levels start to decline from their earlier peaks about eight months after the second dose. After a third shot, antibody levels were up more than five times among people ages 18 to 55 and more than 11 times in people ages 65 to 85, compared with two doses. U.S. Surgeon General Vivek Murthy, has also cited current data made available by vaccine providers, including this report during a recent briefing conducted by the White House Covid-19 task force and stated, "Having reviewed the most current data, it is our clinical judgment that the time to lay out a plan for Covid-19 boosters is now."

The vaccines work by generating neutralizing antibodies, which prevent the virus from entering cells and replicating. To test for the current level of antibodies you have as protection from Covid-19 infection, we must first understand the answers to the most frequently asked questions surrounding the facts we have been provided with against the global effort against Covid-19.

  • What are neutralizing antibodies?

Neutralizing antibodies (NAbs) are antibodies that are responsible for defending cells from pathogens, which are organisms that cause disease, such as SARS-CoV-2. They are produced naturally by the body as part of its immune response, and their production is triggered by both infections and vaccinations.

  • What is the importance of neutralizing antibodies as related to SARS-CoV-2?

Neutralizing antibodies can stop SARS-CoV-2 from infecting the body by affecting how the molecules on the pathogen’s surface can enter cells in the body. Neutralizing antibodies are responsible for blocking the entry of SARS-CoV-2 into a cell so that it is unable to infect healthy cells and is unable to replicate and cause severe infection.


  • Why are vaccines important for the production of neutralizing antibodies?

Vaccines are designed to mimic a natural immune response to an infection. The immune system can be triggered to produce neutralizing antibodies in response to the virus or bacteria in the vaccine, which will then recognize and fight SARS-CoV-2 naturally if the person is exposed to the virus.

  • What are titers?


A titer is a measurement of the amount or concentration of a substance in a solution. It usually refers to the number of antibodies found in a person's blood. Lab tests that involve titers measure the presence or amount of an antibody in the blood and are used to improve immunity, prove exposure, and vaccine efficacy.

  • What is a serology or antibody test?

A serology test, also referred to as an antibody test is used to detect the presence of antibodies against a pathogen such as SARS-CoV-2.

  • Are serology tests used to diagnose active COVID-19?

No, serology should not be used to diagnose active COVID-19, because it does not detect the virus itself, but detects antibodies that the immune system develops in response to the virus. It should not be used to diagnose acute SARS-CoV-2 infection, as the antibodies could not be generated in a short time period.

  • What are the types of serology tests for COVID-19?

Serology tests are generally categorized as qualitative or quantitative. Qualitative serology tests provide a simple “yes” or “no” answer to whether a person was once infected with SARS-CoV-2.

Quantitative serology tests, such as enzyme-linked immunosorbent assays (ELISAs) provide more detailed information, such as levels of antibodies in a test sample. Quantitative tests are generally more accurate than qualitative tests, partially due to the detailed data generated. Serology Tests;

  1. Detect antibodies in a person’s blood that bind to specific antigens on the SARS-CoV-2 virus.


  1. Can be qualitative (yes/no, positive/negative) or quantitative (how many antibodies, how reactive). Quantitative tests can be more accurate but are generally more useful for research purposes. Qualitative tests, like lateral flow assays, can be performed very quickly at the point-of-care

  • What is the SARS-CoV-2 Neutralization Antibody Test?

The SARS-CoV-2 Neutralization Antibody Test is the first semi-quantitative commercial test with FDA emergency use authorization that can directly detect circulating neutralizing antibodies against SARS-CoV-2.

  • How does the SARS-CoV-2 Neutralization Antibody Test work?

The test uses the interaction between viral protein-receptor protein to mimic the virus infection of a live cell, which is monitored by a chromogenic reaction. When there are neutralizing antibodies in the patient sera, they will block the specific protein-protein interaction and hence reducing the chromogenic reaction, mimicking the virus neutralization process.

  • How is the SARS-CoV-2 Neutralization Antibody Test different from other antibody tests?

The SARS-CoV-2 Neutralization Antibody Test detects COVID-19 vaccinated people whose COVID-19 mRNA vaccines induce neutralizing antibodies specific to the S1 spike protein. The SARS-CoV-2 Neutralization Antibody Test detects the amount of neutralizing antibodies present in the body that was generated from the vaccine.

Other antibodies or serology tests target nucleocapsid proteins that are likely detected only after natural infections. This is the only FDA EUA approved test to determine whether you have functional neutralizing antibodies. Other IgG/IgM antibody tests do not provide results on the functional or neutralizing aspect of the antibodies.

  • Why does the SARS-CoV-2 Neutralization Antibody Test target the S1 spike protein?

The SARS-CoV-2 Neutralization Antibody Test identifies the receptor-binding domain (RBD) of the S1 spike antigen to detect antibodies that block the virus entry into the cells. This identification is aligned with the multiple vaccines currently used that target or include the SARS-CoV-2 S1 RBD, with the goal of producing a protective antibody. The SARS-CoV-2 Neutralization Antibody Test detects antibodies to the S1 RBD antigen which are relevant to vaccines incorporating this immunodominant region with the goal to elicit neutralizing antibodies in vaccinated people.

  • What is the importance of SARS-CoV-2 neutralizing antibodies?

The presence of neutralizing antibodies has been shown to correlate with protection from viral infection. Most of the SARS-CoV-2 vaccines in use or under investigation aim to produce neutralizing antibodies specific for the spike protein on the outside of the virus particles.

Neutralizing antibodies against the spike protein can prevent the interaction between the virus and our cells and help eliminate an infection during its early stages. Measuring the abundance of these antibodies is one of the key parameters for evaluating SARS-CoV-2 vaccines.

  • Should the SARS-CoV-2 Neutralization Antibody Test be used to determine immunity status?

No, the test should not be used to determine a person’s immunity status or protection from COVID-19. The SARS-CoV-2 Neutralization Antibody Test should be used as a reference as to the level of neutralizing antibodies present in the body.

If the results of the antibody test are interpreted as an indication of a specific level of immunity or protection from SARS-CoV-2 infection, there is a potential risk that people may take fewer precautions against SARS-CoV-2 exposure.

  • How should the SARS-CoV-2 Neutralization Antibody Test results be interpreted?

The quantitative reporting is expressed as a % Inhibition with 30% as the cutoff point for positive neutralizing antibodies present in the body. Periodic testing over time will provide an individual with a trend line in the level of neutralizing antibodies present in the body.

  • Does the SARS-CoV-2 Neutralization Antibody Test have a Food and Drug Administration (FDA) issued Emergency Use Authorization (EUA) pursuant to Section 564 of the Federal Food, Drug, and Cosmetic Act (21 U.S.C. 360bbb-3?

Yes, the FDA issued an EUA on November 6, 2020, intended for use as an aid in identifying individuals with an adaptive immune response to SARS-CoV-2, indicating prior infection.” The SARS-CoV-2 Neutralization Antibody Test has been authorized only for the detection of antibodies against SARS-CoV-2, and not for any other viruses or pathogens. This test is authorized for the duration of the declaration that circumstances exist justifying the authorization of emergency use of in vitro diagnostics for the detection and/or diagnosis of COVID-19 under Section 564(b)(1) of the Act, 21 U.S.C. § 360bbb-3(b)(1), unless the authorization is terminated or revoked sooner.

  • What are the efficacy rates of the various vaccines?


  1. Pfizer-BioNTech: 95%

  1. Moderna: 94.1%

  1. Johnson & Johnson: 72% (Single Dose)


  1. Astra Zeneca: 76% (Pending authorization use in the U.S.)

  1. Novavax: 89.3% (Not currently used in the U.S.)

It is important to note that it’s not possible to make direct comparisons between these COVID-19 vaccines. This is because the clinical trials;

  1. used different protocols



  1. included various pools of people across many geographic locations

  1. were carried out at different points in the pandemic

  1. The FDA notes that the only way to directly compare the efficacy of the three vaccines is to conduct a head-to-head clinical trial. This has not yet been done.

  • Who should get tested for neutralizing antibodies?


Anyone who has taken a COVID vaccine and wants to determine whether your body produced neutralizing antibodies in response to the vaccine. For a vaccine that is 95% effective, 5,000 out of every 100,000 people vaccinated won't be protected. As a priority, people who were first vaccinated such as the elderly over age 75, people in congregate living facilities, front-line essential workers, healthcare workers, educators, and the people with immunocompromised should be prioritized.

  • Why should a person get tested for neutralizing antibodies if already been vaccinated?

Antibody levels wane over time and it may be useful to periodically track your level to determine the need for a follow-up “booster” shot.

  • CDC recently issued guidance for booster shots. Should I get a neutralizing antibody test even though it is recommended to get a booster shot?

Yes, you may want to consider a neutralizing antibody test to determine your level of correlates of protection. Based on your health status and elapsed time passed since your last vaccine dose, knowing your correlates of protection may assist you in making an informed personal health decision.

Knowing the current level of protection you have against infection through the measurement of antibodies helps to make a conscious decision as to why you may need a third dose of the vaccine. As it is, the booster effort is expected to be available come the week of September 20, 2021, assuming the FDA and the CDC sign off on the safety and effectiveness of the doses by that point and will likely mirror the original vaccine rollout, with health care workers, nursing home residents, and people over age 65 first in line.

The rest of the population, young adults ages 18 and older will be eligible for a third dose of either the Moderna or Pfizer-BioNTech shots are eligible for booster shots within eight months after their second dose. The immunocompromised are recommended to obtain their booster shots as early as the first rollout of the third dose, health officials have also advised.

There are two studies published by the CDC on August 18, 2021, that provides a broader view

of the current data on vaccine effectiveness, including some research the agency said indicates the vaccines are beginning to show a decrease in the ability to curb infection or evidence of waning immunity.

In the New York study, researchers found the vaccines were 92 percent effective in preventing COVID infections in May, but just 80 percent effective by late July. In the second study, CDC looked at people living in nursing homes, finding the shots' ability to prevent infections in such patients declined from 75 percent in March to just over 50 percent in early August.

A fair point has not been stressed so clearly, until now.

Covid-19 vaccines are working very well to prevent severe illness, hospitalization, and death, even against the widely circulating Delta variant. However, with the Delta variant, public health experts are starting to see reduced protection against mild and moderate disease. If we were to win against Covid-19, the right move is to stay ahead of the virus.

Vaccines protect against the severity of Covid-19 infection including its variants. The studies are there, the results can be seen. The data provided has backed research that the current vaccines appear to work well against variants of concern that have emerged so far. Yet they may not work as strongly against newer variants as they do against earlier ones.

This is not the last round of the fight with SARS-CoV-2, we can only hope to expect several more challenges from the virus in the years to come. Existing mutations could combine in “new and scary ways. This is not the time to be divided. A unified forward thinking approach is what we need to get ahead of the threat.

This is the reason people need booster shots. To ensure they get the fullest level of protection possible against the variants from follow-up shots that intend to safeguard against viral mutations and waning immunity.

While the US and the rest of the world hopes the virus will get weaker with time, there is a vast majority that thinks the virus is “here to stay” and those that belong to high-risk populations will need regular boosters to stay protected. People want the promised efficiency of a third dose against any variants that emerge and are better able to evade current vaccines.

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