Timing and degree of neutralizing antibody development after pfizer-biontech vaccination

ABSTRACT

INTRODUCTION: Most adults receiving mRNA vaccines for SARS-CoV-2 (SCV2) exhibit IgG antibodies (Ab) targeting the S1 spike protein within a week of dose 2. However, correlates of protection are still not fully understood. The aim of this study was to better quantify the % of neutralizing Ab (nAb) that develop after dose 2 and also identify factors affecting the timing and degree of nAb production. METHODS: Using a fluorescence immunoassay to quantify the % of SCV2-Ab capable of blocking S1 at its receptor binding domain (for attaching to ACE-2 receptors), residents/ staff (n=70;ages 23-100 yrs) of an assisted living facility had blood samples measured on day 7 and 21 following dose 2 of the Pfizer-BioNTech mRNA vaccine. Based on existing research, %nAb < 30% is delineated as inadequate protection (“nAb negative”). RESULTS: Except for a 58 yo man taking daily prednisone (asthma) and a 55 yo man on levothyroxine, 100% of those < 70 yrs (n=33) were nAb+ (>30% nAb) on day 7 after dose 2. However, if >70 yo (n=37), the % of nAb+ findings diminished with age. Only half of those 71-80 yo, 33% of those 81-90 yo and 11% of those >90 yo were nAb+. Nonetheless, 2 weeks later, the %+ among those tested had increased to 83%, 71%, and 50% for those respective age groups. When examining the average of nAb% measurements within each of the various age group stratifications 1 week after dose 2, the averages ranged 96-100% for the 3 age groups < 50 years (ie, 23-30, 31-40 and 41-50), while the age group averages were borderline or inadequate for those >70 yo. However, 21 days after dose 2, 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 persons > 90 yo (n=8), the average %nAb was 35% but half of those persons (n=4) had no detectable nAb, either at day 7 or day 21. No persons had any significant declines in %nAb between Day 7 and 21 and the majority sustained or improved their %nAb. CONCLUSIONS: Escalating age and immunomodulating medications/conditions do impact the timing and degree of nAb developing after mRNA vaccination. Most persons < 90 yo are observed to be “positive” for protective levels of nAb by 3 weeks after dose 2. On-going investigations are addressing the duration and sustained degree of nAb+ findings as well as external validation of the tool used in this research.