The National Cancer Institute's (NCI) Serological Sciences Network (SeroNet) has been at the forefront of understanding immune responses to SARS-CoV-2 and COVID-19 vaccines since April 2020. SeroNet's research encompasses various aspects, from antibody duration to vaccine effectiveness in specific populations, providing crucial insights for public health strategies.
Antibody Response and Duration
SeroNet studies indicate that the majority of individuals who have recovered from COVID-19 or have been vaccinated develop neutralizing antibodies against the virus. A study showed that all 25 participants had detectable neutralizing antibodies 57 days after a single dose of the Janssen/Johnson & Johnson vaccine. According to Dr. Samantha Finstad, a SeroNet leader, antibodies to SARS-CoV-2 last for at least several months. One study found that people with mild to moderate COVID-19 had neutralizing antibodies for at least 5 months, while another showed similar results for 6 months.
Furthermore, a separate SeroNet study revealed that nearly all participants who recovered from COVID-19 had memory B cells targeted to SARS-CoV-2, suggesting a lasting immune response. Memory B cells can remain in the body for years and rapidly produce more antibodies upon re-exposure to the virus.
Correlates of Protection and Standardization
Determining the level of COVID-19 antibodies needed for protection against future infection is an ongoing area of investigation. NCI is addressing the challenge of comparing antibody level measurements between studies with the SARS-CoV-2 serology standard. This standard allows researchers to compare antibody levels across different studies, even when using different antibody tests. Dr. Juli Klemm, another SeroNet leader, mentioned that researchers at the Frederick National Laboratory for Cancer Research have calibrated the standard to a unit of measure approved by the World Health Organization, advocating for its use in international studies.
Vaccine Effectiveness in Cancer Patients
Emerging evidence suggests that some cancer patients may not mount a strong response to COVID-19 vaccines. Several SeroNet groups are monitoring vaccinated cancer patients to measure their immune response over time. The CDC recommends an additional dose of the same mRNA vaccine for moderately to severely immunocompromised individuals, including those actively undergoing treatment for blood cancer, those who have received a stem cell transplant within the last 2 years, and those taking immunosuppressive medications.
Dr. Finstad emphasized that vaccine effectiveness varies among cancer patients, with those having blood cancers or undergoing immunosuppressive therapies showing less robust antibody responses. However, cancer survivors in remission are more likely to mount a strong immune response to the vaccine.
Role of T Cells
While antibodies are a primary focus, SeroNet also studies the broader immune response to SARS-CoV-2, including the role of T cells. Studies suggest that T cells contribute to protection from infection, as demonstrated in nonhuman primates lacking T cells being more susceptible to reinfection with SARS-CoV-2. Further research is needed to fully understand the T-cell response to COVID-19.
Protection Against Variants
Antibodies from vaccinated individuals generally react with SARS-CoV-2 variants in lab tests. Plasma from vaccinated people or those who recovered from COVID-19 neutralized the alpha variant. Individuals who received the Johnson & Johnson vaccine appear to produce antibodies that can neutralize several different variants at varying levels. A new SeroNet study indicates that individuals who recovered from COVID-19 or were vaccinated with the Moderna or Pfizer vaccines are still protected against the delta and kappa variants, although the protection is less than that of the original virus.
Insights into Disease Severity and Spread
SeroNet studies have found correlations between immune system responses and disease severity. People with high levels of COVID-19 antibodies tend to have milder disease. Differences in immune responses were also observed between children with mild and severe COVID-19 and those who did and didn’t develop multisystem inflammatory syndrome (MIS-C). Antibody studies have also provided insights into the spread of the coronavirus, revealing evidence of SARS-CoV-2 infections in the United States as early as January 2020 and confirming disparities in COVID-19 infection rates among different racial and socioeconomic groups.
