60 Presence and Degree of Neutralizing Antibody Production Following Pfizer-BioNTech Vaccination

Study Objectives: While almost all adults vaccinated with the SARS-CoV-2 mRNA vaccine become positive for the IgG antibody (Ab) targeting the spike protein of SARS-CoV-2 within a week of their second dose, correlates of protection for SARS-CoV-2 are not fully understood. Therefore, the primary purpose of this study was to attempt to quantify the percentage of SARS-CoV-2 neutralizing antibodies (nAb) that develop after dose 2 vaccinations and also identify any factors that might affect the timing and degree of nAb production. Methods: A fluorescence immunoassay analyzer was used to quantify the percent of SARS-CoV-2 antibodies capable of blocking the spike protein at its receptor binding domain (RBD) for attachment to ACE-2 receptors. Seventy residents and staff of an assisted living facility ranging in age from 23 to 100 years were enrolled. Fingerstick blood samples were measured at seven days and 21 days following the 2nd dose of the Pfizer-BioNTech mRNA vaccine. Based on prior research, nAb measurements 30% nAb) on day 7 after the 2 nd vaccine dose. However, among the 37 patients older than 70 years, the percent of persons positive for nAb (>30%) on Day 7 diminished with age. Only half of those 71-80 yo, 33% of those 81-90 yo and 11% of those >90 yo were positive for nAb. Two weeks later, however, the percentages among those tested had increased to 83%, 71%, and 50% for those respective age groups. Also, one week after the second vaccine dose, the average neutralizing Ab% measurement (%nAb) among the various age groups under the age of 50 years ranged from 95 to 100% while age group averages were borderline or inadequate for those older than 70 years. Nevertheless, 21 days after the second dose, the average %nAb measurement had become 91% for those 61 to 70 years of age, 75% for those 71-80, and 55% for those 81-90. For the eight persons over 90 years of age, the average %nAb was 35% and half of those persons (n=4) had no detectable nAb, either at day 7 or day 21. No persons had significant declines in the %nAb measurements and the majority sustained or improved their %nAb between Day 7 and Day 21. Conclusions: Escalating age and immunomodulating medications and conditions can impact the timing and degree of neutralizing Ab produced following SARS-CoV-2 mRNA vaccination. Most persons under the age of 90 years were considered to be “positive” for protective levels of nAb within three weeks following the 2nd dose of the SARS-CoV-2 mRNA vaccine. On-going investigations involve evaluations of the duration and sustained degree of positive nAb findings, as well as external validation of the tool used in this current research.