Neutralizing antibody response to COVID vaccination among the young and the elderly

ABSTRACT

Objective: The objective of the study was to assess the levels of neutralizing antibody after COVID vaccination in the elderly and compare it with that of the younger persons. The study also aimed at determining the association between the age, sex, and comorbidities and levels of neutralizing antibodies in the young and the old. Subjects and Methods: This was a single-center, cross-sectional, analytical study, conducted in the General Medicine Unit of ACS Medical College, Chennai, from August 2021 to October 2021. Forty?five elderly persons aged 60 years and above and 103 young adults aged 18 years and above and <60 years who were vaccinated with either COVISHIELD or COVAXIN were randomly selected to participate in this study. A detailed history regarding vaccination status, vaccination type, comorbidities, and breakthrough infection was obtained. Blood samples were collected from the participants to analyze the levels of neutralizing antibodies developed after COVID vaccination. Results: The mean age of the older participants was 66.13 ± 5.3 years and the mean age of the younger participants was 36.48 ± 10.9 years. The median level of neutralizing antibody in the younger participants was 97.4% (interquartile range [IQR] 96.4%–98.0%) and in the older participants was 97.1% (IQR 93.1%–97.6%). There was a significant difference in the neutralizing antibody level between the younger and the older participants (P = 0.033). There was no significant difference in the neutralizing antibody levels after two doses of either of the two vaccines among both the groups of participants. There was no significant association between the neutralizing antibody titer and sex and comorbidities in both the groups of participants. Five young and two old participants had breakthrough infections after vaccination. The antibody level was higher in persons with breakthrough infection than in those with no breakthrough infection in both the study groups. Conclusion: There was a significant difference in the neutralizing antibody level between the younger and the older participants after COVID vaccination. No significant difference existed in neutralizing antibody response with respect to the type of vaccine in both the study groups. There was no significant association between sex, comorbid status, and neutralizing antibody levels in both the groups.