Declining vaccine antibody levels require more dynamic immunity assessments 

Immunity against Covid-19 is more complicated than the binary yes-or-no of vaccination status or the presence of antibodies. While vaccine protection against hospitalization and severe disease remains high, a small but significant number of fully vaccinated individuals are experiencing breakthrough infections. As we enter the second fall of Covid-19, we are faced with a more complex phase of the pandemic as organizations return to work, students return to school, and new federal mandates for vaccinations, boosters and testing go into effect. For many, the most valuable asset at this time is assurance: a real understanding of risk to make personalized and informed decisions about what to do, where to go and what precautions to take. 

Understanding Individualized Levels of Protection   

Immediately following a two-dose vaccination with Moderna or Pfizer mRNA vaccines, most non-immunocompromised individuals will generate high levels of neutralizing antibody levels (NAbs) and significant protection against infection and severe symptoms. Unfortunately, these decline with time, an average of 75% after six months, according to recent data.  

Following this decline, NAb levels are still sufficiently high and provide over 80% protection for Moderna and Pfizer patients against the wild-type Covid-19 strain – the initial virus first detected in January 2020. However, every new mutation of the virus carries the potential for additional deviation. As the vaccine-resistant and highly contagious Delta variant continues to spread and cause severe illness as the dominant strain in the United States, Moderna and Pfizer antibodies appear to be about 4-fold less efficient at neutralizing the mutated variant. Notably, the estimated average vaccine efficacy for the wild-type and Delta variant against infection deviates between the two vaccines over time: between months seven and eight, vaccine efficacy for Pfizer drops below 50% while Moderna is predicted to drop below 50% around 10 months post-vaccination. 

For the immunocompromised, this situation is even more concerning. Many factors play into just how protected a person is from Covid-19 infection. On top of vaccination status, factors like age and genetics can influence immune responses in individuals. On top of that, lifestyle differences, like smoking, nutrition, and the environments where we live, can also factor in. People with conditions that limit their immune responses or those taking immune-suppressing drugs are particularly at risk for reduced protection even following vaccination, making it important to regularly monitor their protective immunity.

The good news is that new options do exist that can give us this more granular understanding: semiquantitative immunity tests that not only identify Covid-19 antibodies but provide direct, individualized measures of neutralizing antibody levels, indicating protection against infection and severe symptoms. 

Using NAb Levels as a Guide 

Historically, protection against hospitalization and severe disease was considered the key measure of vaccine success – and the vaccines we have today certainly pass that test. However, given the large percentage of people that remain unvaccinated, the threat of more severe mutations, and evidence that the vaccinated can experience breakthrough infections and still spread the virus, Covid-19 will likely be a going concern for months or years to come. If we are to return to normalcy, maintaining high levels of NAb protection against Covid-19 infection will be critical to ensuring the safety of schools, workplaces and communities. 

Using tests that look at current immunity levels can help individuals make their own informed health decisions and paint a broader picture of holistic viral activity for organizations looking to mitigate spread. For individuals, understanding the level of our protection can be the simplest way to assess the need for a booster dose, in consultation with a physician. For organizations – especially those in the process of mandating vaccination – antibody assessments can act as an additional offering to support their teams. This can be especially important for occupations with in-person customer engagement, so employees can gain the insights they need to make the right decisions for themselves and take necessary precautions. 

Vaccinations continue to be our most critical tool in the battle against Covid-19. While antibody testing is not currently recommended by the CDC to estimate vaccine protection and the FDA has just begun to authorize booster shots for select groups, the past 18 months have shown us that our relationship with Covid-19 and mitigation priorities can change rapidly. As more vaccinated Americans reach the point where studies show efficacy may decline, these tests can provide important guidance and peace of mind.  

As we look toward this future, knowledge of our protective immunity status will help all of us make better, more informed decisions. To do this, we must make antibody assessments more widely available so we can better understand our level of risk – and what we need to do to keep ourselves and others safe as we look to return to our offices, schools, and normalcy.

Photo Credit: RLT_Images, Getty Images

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